Landracing Forum
Tech Information => Technical Discussion => Topic started by: gasblender37 on January 15, 2015, 01:08:26 PM
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Please comment....
My thoughts and questions on the engine.
Basic Engine:
Ford 5.4 L Racing Block – 3.5512” Bore, Deck Height 10.079”
Aftermarket Billet Crank – 3.24” Stroke = 257 ci
Manley 5.4 L 6.657” Pro I Beam Rods which gives a 2.05 Rod Ratio
Aftermarket Pistons with compression height of 1.80” using Zero Deck Height
Ford DOHC “B” Heads
MMR Purpose Built EFI Intake Manifold with Dual Injectors (16, 1 For Each Port)
One large Turbocharger
My thoughts:
Using tall deck 5.4 L block and 5.4 L Rods instead of 4.6 L Block and 4.6 L Rods will give a high rod ratio (2.05) which would be beneficial on the top end and less stress on the rotating assembly.
Using Ford DOHC “B” Heads because they are readily available and would require no porting. The knock on these heads is the lack of intake manifold availability and only 8 injectors for the 16 port manifold. The MMR manifold solves these issues.
My Questions:
Does the build sound rationale?
Would the 1.80” piston compression height be a problem?
What static compression ratio would I use?
What size turbo?
What camshaft specs?
Thanks,
Skip
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Well..... if it were me......
I'd use a 4.6 iron block (8.937 deck ht)
If you are going to use a billet crank might as well have it made to use WIDELY available chevy rods.
Use a 3.250 stroke and choose a rod journal you like: 1.880, 2.000, or 2.100.
All kinds of rod lengths out there with the basics being 5.700, 5.850, 6.000, 6.125, 6.200 right off the bat.
And if your worried about the rod/stroke ratio (I wouldn't) it's around 1.8 to 1.9 which is fine.
You 1.800 compression height is a killer for piston weight. With the 3.25 stroke & a 6.00 to 6.125 rod your compression height would be 1.312 to 1.187. lighter piston but still enough room for a durable ring pack.
I run more compression than most but I would run at least 9.0:1 (my current car is 10.5:1) Yes with turbos...
As for the rest, we can't tell you everything, what fun would that be? :cheers:
Good luck & have fun.
Who holds that E/BGR record anyway........ :-D
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Dynoroom,
Thanks for the reply. The current record is held by:
E Holmes-Kugel-McGinnis Jo. Kugel 08/96 236.036
My thinking is that back in 96 no one was using a Ford DOHC engine. Might be an advantage today in breaking the record. I was also thinking of a 10:1 CR
Thanks again
Skip
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Right.
I'll bet WAY back in '96 the engine builder used a 305 Chevy block bored to 3.750. then off set ground a 3.00 stroke crank to 2.910 to build a 257" motor. He might of had to notch the top of the bores for the exhaust valves to clear too.
I think your 4 valve idea is good.
Remember to have fun along the way..... :-)
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I like your idea of the 4.6 block. Might save a little money rebuilding a used cobra block. Are the 6.2 chevy rods available with 1.88 rod journals? I heard there might be some advantage in using a smaller rod journal?
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.....I'll bet WAY back in '96 the engine builder used a 305 Chevy block bored to 3.750. then off set ground a 3.00 stroke crank to 2.910 to build a 257" motor. He might of had to notch the top of the bores for the exhaust valves to clear too. ....
....and I wonder who that builder might of been 8-) 8-) 8-) :-o :-o :-),
Sum
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I agree Sum, may have some input here.
DW
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I wonder if the 4.6 would fit better under the hood. That 5.4 is huge engine, something else to think about.
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If you are spending money on billet or aftermarket rods (like r&r or the sort) the cost will be around the same for whatever rod length, pin and crank size you want. Especially for the power you are thinking.
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What about a 4.8 LS with smaller crank? No need to mess with the DOHC/chain
setup, they'll handle immense amounts of power under boost and parts are not
only readily available but getting "cheap"...
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Gentlemen,
Thanks for all the great input. You guys have caused me to re-think my plan. "Sometimes you get what you want and it is not what you expect."
Skip
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3.905 x 3.18==304.6
Camaro "slightly overbored" pistons, 2" crankpin de-stroked 4.8 crank
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Well..... if it were me......
I'd use a 4.6 iron block (8.937 deck ht)
If you are going to use a billet crank might as well have it made to use WIDELY available chevy rods.
Use a 3.250 stroke and choose a rod journal you like: 1.880, 2.000, or 2.100.
All kinds of rod lengths out there with the basics being 5.700, 5.850, 6.000, 6.125, 6.200 right off the bat.
And if your worried about the rod/stroke ratio (I wouldn't) it's around 1.8 to 1.9 which is fine.
You 1.800 compression height is a killer for piston weight. With the 3.25 stroke & a 6.00 to 6.125 rod your compression height would be 1.312 to 1.187. lighter piston but still enough room for a durable ring pack.
I run more compression than most but I would run at least 9.0:1 (my current car is 10.5:1) Yes with turbos...
As for the rest, we can't tell you everything, what fun would that be? :cheers:
Good luck & have fun.
Who holds that E/BGR record anyway........ :-D
x2
Also:
What engine rpm range do you plan to use? At high rpm heavy pistons are a BAD idea. Calculate the max piston acceleration and the rod pin end load to make an intelligent choice.
Smaller rod journal diameter can reduce parasite drag significantly. You need to pick a size where a quality bearing is available.
I would be VERY CAREFUL about using a rod/stroke ratio > 1.9/1 with 4 valve heads, unless you want an F1 type power curve. With good low and mid lift flow from 4 valve heads, you are going to want to ADVANCE the point of peak flow demand. Longer rod/stroke ratio DELAYS this.
The 'C' type heads (tumble type) are known for higher top end bhp.
Higher static compression ratio is the way to go. You will surely need to run a wastegate.
Give some serious thought to this, BEFORE committing to expensive custom parts. Engineering analysis and computer simulation is WAY CHEAPER than a pile of expensive parts that do not do what you wanted them to do . . . . . .
:cheers:
Fordboy
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If you are spending money on billet or aftermarket rods (like r&r or the sort) the cost will be around the same for whatever rod length, pin and crank size you want. Especially for the power you are thinking.
True, you can get almost any combination you want but ordering a commonly used specification will result in shorter wait times, less frustration and lower prices.
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Are the 6.2 chevy rods available with 1.88 rod journals? yes
very common in cup and on Ebay
http://www.ebay.com/sch/i.html?_sacat=0&_nkw=6.200+rods&_frs=1
http://www.ebay.com/itm/Set-of-8-Carrillo-H-Beam-6-200-Rods-NASCAR-ARCA-NHRA-L-K-Engine-Builders-/151306895026?pt=Motors_Car_Truck_Parts_Accessories&hash=item233a97feb2&vxp=mtr
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Fordboy,
Would you elaborate a little more on:
F1 type power curve. ADVANCE the point of peak flow demand. Longer rod/stroke ratio DELAYS this.
Thanks,
Skip
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Fordboy,
Would you elaborate a little more on:
F1 type power curve. ADVANCE the point of peak flow demand. Longer rod/stroke ratio DELAYS this.
Thanks,
Skip
Skip,
F1 type power curve:
Current Cup engines are running rod/stroke ratios in the 1.7/1 to 1.83/1 range. Unrestricted long track engines are producing peak power @ approx. 9500 rpm. They would be running 10,000 rpm, or more, if they could. Raising the rod/stroke ratio to 2.05/1 on an engine 100 cubic inches smaller, and with 4 valve heads, is going to drive the power peak to ~11,500/13,000 rpm, unless the valve motion/flow potential is severely restricted. Is this what you want to accomplish? Not if you are planning to turbo charge it.
ADVANCE the point of peak flow demand.
Flow demand/piston demand is a function of build geometry, and is calculated as the displacement in cubic inches (or whatever) * efficiency ratio (Volumetric efficiency) relative to crankshaft motion in degrees.
Piston motion, ie displacement, velocity and acceleration is not uniform, and it is not symmetrical to 90 ATDC. This is due to "the cosine effect" of the geometry. The crankshaft's rotation displaces the con-rod big end laterally during operation, effectively shortening and lengthening the con-rod, thereby altering uniform piston motion. For V-8s of typical geometry, @ 90 ATDC the piston will have traveled more than half the stroke. Way more, like 5 to 8% or so. Radical geometry combinations can drastically impact piston motion.
So since the piston travel is not uniform, peak flow demand usually occurs between 70 to 80 ATDC. The peak demand is closer to TDC with shorter rods.
Longer rod/stroke ratio DELAYS this.
A longer rod has the opposite effect, and peak demand is delayed by some amount of crankshaft degrees. The geometric effect can vary based on the difference in length.
So what?
Depending on the flow characteristics of the inlet tract and the motion of the valve train, a savvy builder might want to alter/take advantage of the flow/piston demand.
For example: 4 valve/cyl heads are going to have superior low/mid lift flow compared to 2 valve/cyl heads.
1) Fulfilling demand sooner will probably benefit a 4 valve combo by allowing the closing of the intake valve "sooner".
2) Delaying demand will probably benefit a 2 valve combo, by giving the inlet tract time to "catch up".
3) Etc.
Be aware that it is not just flow demand that is altered here. Requisite valve events are altered as well.
BTW: This is a very complex subject, about which not all engineers/engine builders agree. I suggest you obtain some of the collegiate textbooks from the reading list on my tech thread: How do I make my engine better, Racing Engines 101. C. F. Taylor is where I would suggest you start.
Also: Since your engine will be a "blower engine" you will receive some advice that "none of this matters". Think very carefully about that. I suggest that instead of thinking of your engine as a "blower engine" or "turbo engine", think of it instead as a normally aspirated engine operating in a "high air density environment". JMO.
:cheers:
Fordboy
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Also: Since your engine will be a "blower engine" you will receive some advice that "none of this matters". Think very carefully about that. I suggest that instead of thinking of your engine as a "blower engine" or "turbo engine", think of it instead as a normally aspirated engine operating in a "high air density environment". JMO.
:cheers:
Fordboy
This is so very true. No matter what the engine type.
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Ding, ding, ding...we have a winner. Fordboy, you just have filled in a mystery for me!
If you look at the evolution of OEM performance motorcycles over the past 10 years, you notice that peak HP has been moving higher in terms of rpm. The rod/stroke ratio has also been moving higher. Furthermore looking at different bike classes, the smaller bikes (600cc) have a rod/stroke ratio in the 2.1 range with a peak power around 15K, the S1000rr has a rod/stroke ratio at a tad over 2.0 with a peak of 13.5K, while the 'Busa has a peak around 10.5K with a rod/stroke of 1.83.
(without getting in too much detail for a forum post) The mystery for me is why when stroking a Busa motor it is progessively more difficult to keep the peak HP at the same RPM as the stroke increases. Even with higher flowing heads, bigger cams, better exhaust: The power goes up, but the peak rpm slowly drops as the stroke increases (as the rod ratio drops). You can see it with cam timing, the "sweet spot" keeps moving lower in the rpm range. Now of course you make more power with a bigger engine, but the peaks (for TQ and HP) creep lower as the stroke increases.
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The mystery for me is why when stroking a Busa motor it is progessively more difficult to keep the peak HP at the same RPM as the stroke increases. Even with higher flowing heads, bigger cams, better exhaust: The power goes up, but the peak rpm slowly drops as the stroke increases (as the rod ratio drops). You can see it with cam timing, the "sweet spot" keeps moving lower in the rpm range. Now of course you make more power with a bigger engine, but the peaks (for TQ and HP) creep lower as the stroke increases.
As you stroke engines, usually what happens is: the rod becomes shorter by necessity. That is going to have the impact you describe. The only way to retain rod length would be to increase the height of the block and/or shorten the compression height of the piston. Not sure how easy this might be on bike engines.
:dhorse:
F/B
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We retain the same rod length by effectively increasing the block length by 1/2 the stroke increase, however that still makes the ratio smaller.
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We retain the same rod length by effectively increasing the block length by 1/2 the stroke increase, however that still makes the ratio smaller.
Yes.
How feasible is it to increase the block height enough to use a longer rod that retains the original rod/stroke ratio?
F/B
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Fordboy,
Thanks for all your insight.
Skip
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Ding, ding, ding...we have a winner. Fordboy, you just have filled in a mystery for me!
If you look at the evolution of OEM performance motorcycles over the past 10 years, you notice that peak HP has been moving higher in terms of rpm. The rod/stroke ratio has also been moving higher. Furthermore looking at different bike classes, the smaller bikes (600cc) have a rod/stroke ratio in the 2.1 range with a peak power around 15K, the S1000rr has a rod/stroke ratio at a tad over 2.0 with a peak of 13.5K, while the 'Busa has a peak around 10.5K with a rod/stroke of 1.83.
(without getting in too much detail for a forum post) The mystery for me is why when stroking a Busa motor it is progessively more difficult to keep the peak HP at the same RPM as the stroke increases. Even with higher flowing heads, bigger cams, better exhaust: The power goes up, but the peak rpm slowly drops as the stroke increases (as the rod ratio drops). You can see it with cam timing, the "sweet spot" keeps moving lower in the rpm range. Now of course you make more power with a bigger engine, but the peaks (for TQ and HP) creep lower as the stroke increases.
Ransome,
increasing the CR seems to help rpm/hp
My Carpenter kit NA 1635 Busa's had climbing hp right up to the 11,500 shiftpoint which i liked = 280-290hp (Dynojet)
But CR was in the stratosphere: 18.3/18.5:1
When i built the motor and measured CR, i didn't believe my numbers and called Bob C.
He listened to my story and said "perfect". :-D
Karl
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Are the 6.2 chevy rods available with 1.88 rod journals? yes
very common in cup and on Ebay
http://www.ebay.com/sch/i.html?_sacat=0&_nkw=6.200+rods&_frs=1
http://www.ebay.com/itm/Set-of-8-Carrillo-H-Beam-6-200-Rods-NASCAR-ARCA-NHRA-L-K-Engine-Builders-/151306895026?pt=Motors_Car_Truck_Parts_Accessories&hash=item233a97feb2&vxp=mtr
If one were to decide to go the used nascar rod route, what would have to be done to the rods to insure reliability?
Thanks,
Skip
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......But CR was in the stratosphere: 18.3/18.5:1.....
At higher rpms on any engine you usually don't fill the cylinder like you do at lower rpm so the dynamic CR probably is going down. Also the cam overlap can really play into the dynamic CR meaning with a big cam you could run much high static CR than with a mild cam. Even though the motor isn't as efficient each cycle at high rpm it is having more of them so can make up for it with more power due to more power strokes per minute with the right combo.
I put a couple pages on my site years ago (still there.... http://purplesagetradingpost.com/sumner/techinfo/tech--dcr%20combinations-1.html ) where people sent me different static CR and dynamic CR engines they had built so one could get an idea if they could get away with a lower octane gas even with a high static CR,
Sum
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......But CR was in the stratosphere: 18.3/18.5:1.....
At higher rpms on any engine you usually don't fill the cylinder like you do at lower rpm so the dynamic CR probably is going down. Also the cam overlap can really play into the dynamic CR meaning with a big cam you could run much high static CR than with a mild cam. Even though the motor isn't as efficient each cycle at high rpm it is having more of them so can make up for it with more power due to more power strokes per minute with the right combo.
I put a couple pages on my site years ago (still there.... http://purplesagetradingpost.com/sumner/techinfo/tech--dcr%20combinations-1.html ) where people sent me different static CR and dynamic CR engines they had built so one could get an idea if they could get away with a lower octane gas even with a high static CR,
Sum
Sumner,
Still a slow and crappy typist, hence the rehash of your post. Sorry, F/B
Translation of Sumner's post into "engineer speak":
At higher rpms on any engine [above the torque peak] you usually don't fill the cylinder like you do at lower rpm so the dynamic CR probably [DEFINITELY] is going down. [The rpm of peak torque is the point of MAXIMUM engine volumetric efficiency.]
Also the cam overlap can [does] really play into the dynamic CR meaning with a big cam you could run much high[er] static CR than with a mild cam.
Even though the motor isn't as efficient each cycle at high rpm it is having more of them so can make up for it with more power due to more power strokes per minute with the right combo. [ABSOLUTELY!!]
I put a couple pages on my site years ago (still there.... http://purplesagetradingpost.com/sumner/techinfo/tech--dcr%20combinations-1.html ) where people sent me different static CR and dynamic CR engines they had built so one could get an idea if they could get away with a lower octane gas even with a high static CR,
[Fuel suppliers "might" be willing to "suggest" the highest dynamic compression ratio a fuel might "tolerate". If you have need to better understand compression ratios, go back and read my post "Compression Ratios, what do they mean?"]
http://www.landracing.com/forum/index.php/topic,12353.0.html
My apologies Sumner.
:cheers:
Fordboy
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Interesting info.
Thanks Mike. :cheers:
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If one were to decide to go the used nascar rod route, what would have to be done to the rods to insure reliability?
Thanks,
Skip
Skip,
Used parts of any type need to be carefully evaluated. Dimensional checking, visual inspection, 'maganflux' or other appropriate particle inspection(s), etc. This goes for the rod bolts as well. Most of the time, I give rod bolts the old "Navy Inspection", ie: chuck them into the nearest deep body of water. Reuse any which float. Reject rod bolts for ANY flaw or dimensional difference. If you find ONE bolt that has been "stretched" beyond the manufacturer's listed length for the part, CHUCK THEM ALL. It's just cheap insurance.
Only consider parts that have been used for ONE race. Otherwise you have NO IDEA of the number of stress cycles to which the part has been subjected.
High stress + Large number of cycles = :dhorse:
:cheers:
Fordboy
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If one were to decide to go the used nascar rod route, what would have to be done to the rods to insure reliability?
Thanks,
Skip
Skip,
Used parts of any type need to be carefully evaluated. Dimensional checking, visual inspection, 'maganflux' or other appropriate particle inspection(s), etc. This goes for the rod bolts as well. Most of the time, I give rod bolts the old "Navy Inspection", ie: chuck them into the nearest deep body of water. Reuse any which float. Reject rod bolts for ANY flaw or dimensional difference. If you find ONE bolt that has been "stretched" beyond the manufacturer's listed length for the part, CHUCK THEM ALL. It's just cheap insurance.
Only consider parts that have been used for ONE race. Otherwise you have NO IDEA of the number of stress cycles to which the part has been subjected.
High stress + Large number of cycles = :dhorse:
:cheers:
Fordboy
Thanks fordboy
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This message bounced because of some safety feature again. Lets see if I saved it.....
Good advice on the connecting rods F/B.
Let me toss this bit of experience out there for others to consider.
back in the 1980's I worked in an engine shop that at the time did Nascar "Busch" series engines. Dale Earnhardt was one of our customers. Anyway, we would replace the rods in these engines after 3-4 races depending. I bought a set of used Carrillo rods from one of Earnhardt's engines. The Carrillo rods we ran used SPS 7/16" rod bolts and in my opinion are second to none. Anyway, magged them and ran them in Duane McKinneys Sundowner twin turbo Corvette for 4 years setting a record @242 mph. Then in my 1400 hp twin turbo small block for 8 years at Bonneville setting several records from 260 to 300 mph in a Firebird.
Mag the rods if they're good I'd use them. Any rod bolts smaller then 7/16 I'd chuck them and get new. In my case I knew the history of the rods & bolts so I was very comfortable with them. But the point is good used parts can work well at Bonneville.
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Dang Mike, you might have almost put another race on them in that amount of time :cheers:
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More thoughts and questions......
Based on the two E Class scenarios below, which one would be the better choice from a piston compression height?
If I wanted to turn the engine at 8000-8500 RPM would I choose the lightest rod & piston weight or some other combo?
Bore Stroke # Cyl Rod Length Cu In Deck Height Rod Ratio Calculated Piston Compress Height
3.5512 3.250 8 6 257.52 8.937 1.85 1.312
3.5512 3.250 8 6.125 257.52 8.937 1.88 1.187
Excuse my ramblings....just trying to get a little bit smarter
Skip
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More thoughts and questions......
Based on the two E Class scenarios below, which one would be the better choice from a piston compression height?
If I wanted to turn the engine at 8000-8500 RPM would I choose the lightest rod & piston weight or some other combo?
Bore Stroke # Cyl Rod Length Cu In Deck Height Rod Ratio Calculated Piston Compress Height
3.5512 3.250 8 6 257.52 8.937 1.85 1.312
3.5512 3.250 8 6.125 257.52 8.937 1.88 1.187
Excuse my ramblings....just trying to get a little bit smarter
Skip
OK, here is the part where it gets "complicated" . . . . . . . .
1) Class displacement limit 260.99 cu. in, I calculate your displacement @ 257.52 cu. in. also, so 98.67% of legal displacement. That's very good.
2) Rod length/stroke ratios vary by 2%, probably not much there, plus the engine is blown. No worries.
3) With a shorter compression height, one might presume a piston would be lighter. This is not necessarily true. The weight (mass) can vary, based on manufacturer and/or application. Generally, (as in normally aspirated) lighter is better. For blown engines with high boost pressures, you definitely want to add mass (weight) to cope with the higher thermal loads on the piston. Piston mfg's (or Dynoroom,) can advise you here. Piston cooling may also be in order . . . . .
4) 8500 rpm with a 3.25" stroke = mean piston speed of 4604 feet/minute high
= max piston speed of 7232 feet minute very high
= max piston acceleration of 142,668 ft/sec^2 extremely high
I have not calculated the rod load yet, and I want to suggest you consider a shorter stroke . . . . . . OR, an rpm change as below:
5) 8000 rpm with a 3.25" stroke = mean piston speed of 4333 feet/minute better, 5.9%
= max piston speed of 6807 feet minute better, 5.9%
= max piston acceleration of 126,662 ft/sec^2 WAAY better, 11.2%
And of course the rod load would be lower. If it was mine, I'd run 7800/8000 rpm max.
For comparison, a 3.25" stroke Cup engine. Keep in mind that Cup engines use very light components, are not blown and have very short service intervals . . . . .
6) 9500 rpm with a 3.25" stroke = mean piston speed of 5146 feet/minute extremely high, 5000 is a typical maximum
= max piston speed of 8083 feet minute extremely high, 8000 is a typical maximum
= max piston acceleration of 178,614 ft/sec^2 beyond extremely high, 150,000 is a typical maximum
Very light weight (as in unobtanium) components and short service life are what makes this combination work. The very thin rings and very tight ring grooves required
to make this combo work, will work against you with a blower engine . . . . . .
7) And of course the big question: How much blower pressure or absolute pressure? ?
There are others on the board that have more experience than I do with blown engines. I would seek out some further advice from them.
:cheers:
Fordboy
edit note: I added in some additional numbers for comparison, segments 5, 6, 7.
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Thanks fordboy. This is exactly the kind of info I am looking for.
Dynoroom. Would you please give me your thoughts?
Thanks,
Skip
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Skip,
You are getting into a "zone" here, where "small" changes can have a big influence on the outcome.
This is why it is important to calculate the numbers, and make decisions based on information, rather than "guessing".
:cheers:
Fordboy
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Thanks fordboy. This is exactly the kind of info I am looking for.
Dynoroom. Would you please give me your thoughts?
Thanks,
Skip
I'm told that dynoroom makes a living out of giving that type of advice, maybe it would be best to call him?? :cheers:
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Thanks fordboy. This is exactly the kind of info I am looking for.
Dynoroom. Would you please give me your thoughts?
Thanks,
Skip
I'm told that dynoroom makes a living out of giving that type of advice, maybe it would be best to call him?? :cheers:
Please excuse my ignorance. I did not know that.
Thanks,
Skip
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Thanks fordboy. This is exactly the kind of info I am looking for.
Dynoroom. Would you please give me your thoughts?
Thanks,
Skip
I'm told that dynoroom makes a living out of giving that type of advice, maybe it would be best to call him?? :cheers:
Please excuse my ignorance. I did not know that.
Thanks,
Skip
Skip,
I wasn't trying to diss you, nope. Sorry if it came across that way.
In a situation much like yours, Mike told me to call him saying that some of this stuff is hard to explain by tapping out text. Much easier when there an active dialog going on. He seems to love talking/tapping about this stuff!
Karl
Mike at 714-5723672
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Karl is right, I do run my own engine building biz. But I have no problem giving MY opinions on engine design & development.....
when I have time. Typing long answers on the forum is not the best way to communicate sometimes complex answers to engine build questions either. So........
The quick answer to your question is QUIT worrying about the optimum rod length. Use the 6" rod as the compression height will work best as you develop the engine. You may also find (I have) that peak power engine speed can be reduced somewhat with a turbocharged engine at Bonneville. Remember you are creating your own air density, and more. This stroke length will have no trouble making power @ 7500 rpm but can run well over 8000 as you develop the system. This is the same stroke Chevrolet used in it's 327" engine, and is also quite common in Nascar Cup engine packages.
I know everyone wants to build the BEST or RIGHT engine the first time. Good luck with that. If the engine type you plan to use has never been run in endurance type racing OR you are using parts that have never been tried before this will be a test. We all go to Bonneville and test our ideas, that's what you are doing too. To show yourself or your peers that your concepts & ideas are right.....
By bringing home a record trophy.
Good Luck with your project 8-)
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x 2
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fordboy and dynoroom,
Thanks again for all your insight. I am a whole lot smarter than I was a few months ago.
"I reckon if this stuff was easy, everyone would be settin' records"
Skip
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My 2 cents, if you are running forced induction, go for the extra compression height. You will need the strength and cooling of the additional volume.
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My 2 cents, if you are running forced induction, go for the extra compression height. You will need the strength and cooling of the additional volume.
x 2
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This applies to naturally aspirated motors and high rpm. It pays to check the intake valve's flow capacity in relation to choke. A fellow can spend lots of bucks to build a bottom end that can withstand rpm to find that the intake valve(s) size limits the revs. The basic engine building software will help with this. I use pencil and paper calcs or PipeMax. There are fancier programs too.
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:cheers:
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Thanks for the great post skip and the equally great thread that followed.
Adding mass to a piston crown above the pin pivot point is always a concern. By de-stroking the motor you are losing a lot of compression and you will want to get some of that back even if it is turboed. There is nothing you can do to the “B” head chambers. In fact there is very little you can do to any mod DOHC head CC because there is absolutely no room. Ford optimized valve size and position right from day 1. You can’t add weld material and you could never mill the surface to make up for the 0.25 de-stroke. So your only choice will be to add a very large mass to the piston crown. How much depends on the manufacturer and forging die. However, a nearly 50% increase in compression height along with increased mass, and maybe increased RPM, makes things seriously worse. I agree with others that cooling and strength are always priorities but you are introducing a new condition that only your piston manufacturer’s expertise will be able to answer.
It’s smart to take advantage of the inexpensive, widely available “B” head. 16 port head works fine with 8 injectors. It is a swirl flow design and the single injector is positioned over the predominant port. Even though both valves are the same diameter the ports flow differently and the short turn radii are different. Since the MMR manifold is fabricated, you could have an extra port welded at the same time in a more central position. You could go with a stock injector position first and then move it to a more central position. Or spend the money on flow bench work. Either way you are the test pilot and having fun!
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Thanks for the great post skip and the equally great thread that followed.
Adding mass to a piston crown above the pin pivot point is always a concern. By de-stroking the motor you are losing a lot of compression and you will want to get some of that back even if it is turboed. There is nothing you can do to the “B” head chambers. In fact there is very little you can do to any mod DOHC head CC because there is absolutely no room. Ford optimized valve size and position right from day 1. You can’t add weld material and you could never mill the surface to make up for the 0.25 de-stroke. So your only choice will be to add a very large mass to the piston crown. How much depends on the manufacturer and forging die. However, a nearly 50% increase in compression height along with increased mass, and maybe increased RPM, makes things seriously worse. I agree with others that cooling and strength are always priorities but you are introducing a new condition that only your piston manufacturer’s expertise will be able to answer.
It’s smart to take advantage of the inexpensive, widely available “B” head. 16 port head works fine with 8 injectors. It is a swirl flow design and the single injector is positioned over the predominant port. Even though both valves are the same diameter the ports flow differently and the short turn radii are different. Since the MMR manifold is fabricated, you could have an extra port welded at the same time in a more central position. You could go with a stock injector position first and then move it to a more central position. Or spend the money on flow bench work. Either way you are the test pilot and having fun!
Saltfever,
Thanks for the kind words. I never thought I would get all of these great comments from the members on this forum. It just shows what a great forum this is!!
Thanks again,
Skip