Landracing Forum
Bonneville Salt Flats Discussion => Build Diaries => Topic started by: delcrossv on November 03, 2023, 09:01:19 PM
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At Stainless' suggestion, I'm going to keep a build diary for this.
Oldest son has an '08 XL that had a lay down with some front end damage so we figured it would be a good time to do an engine build and associated frame mods with the idea of running the bike at Speed Week / USFRA in what is looking like 2025.
New engine started life as a "kinda" SB100 which we picked up as parts. We're keeping the square 4" x 4" bore and stroke.
Came with STD dual carb heads, but testing showed they wouldn't flow more than 250cfm even at .700 lift.
(https://i.imgur.com/qWWbh7A.jpg)
Note the pocketing and lack of squish
(https://i.imgur.com/kiFnK9Q.jpg)
The rear cylinder was scored due to a button failure and I wanted longer skirts than stock SB100 pistons so I called Dan at Axtell for taller ductile cylinders.
Since the bolt pattern was open, we decided to modify Milwaukee 8 heads to match Sporty cam geometry. Also since we're designing the engine for 8000 rpm WOT it's a lot easier to move 4 little valves .570 than 2 big valves .700+
Flywheel spread is an issue so when I ordered the rods from Carrillo, I went longer (7.440) and a 1.500 big end- like an XR. But XR rods are narrower so I was able to find a XL width 1.500 crankpin
Stock sportster pin
(https://i.imgur.com/TkZfJR9.jpg)
XR pin
(https://i.imgur.com/nZK6Dbr.jpg)
The S&S pin we're using. Drive side is welded
(https://i.imgur.com/BSWjZGX.jpg)
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Decided to keep ignition simple so we're going with Morris Magneto. Picked up a older ironhead cam cover off the bay which we're machining to get the oilways to line up.
Case is machined for an alternator which is good as a generator would simply explode at that rpm.
(https://i.imgur.com/x7GV79c.jpg)
I'm drawing a reed valve that will go where the generator shaft would to help evacuate the cam box. Cases already have a reed between the crankcase and sump so between the two it should be well ventilated. Hope I won't need a catch can.
I have a gas Super D carb and an extended bowl but will need to convert it to ethanol. Planning on about 14:1 static compression which should be fine with E98 (or "good" E85)
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Best of luck with the build. It looks like the record is 180mph in M-PF 1650, is that your target? How much power do you think you can make? -Dean
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Hi Dean-
That's the hope.
Here's how I'm figuring it from first principles as I have no good models to work from :
At 8000 rpm the engine will draw about 238 cfm of air. At STP, that's 19.21 lbs/min. Running e98 at 8:1 ( little rich) means the engine will take 2.40 lbs/min of ETOH. that's .36 gal/min. Dividing by 60 gives gal/sec. Multiply by energy density of ETOH (~76000 Btu/gal) gives 462.76 Btu/sec. Convert Btu/sec to HP gives 655 hp @ 100% efficiency. If only! :-D :-D :-D
Figure 45% thermal efficiency (gets a little something from charge cooling) gives about 294 hp- less friction (WAG) losses puts it around 250 or so.. Like an alky drag bike.
So going conservative, better than 200 hp back of the envelope or thereabouts.
Make sense?
We lose 2 psia due to altitude so if a forward facing air scoop is allowed under Nat. Asp.,I can get back toward those sea level numbers.
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Wow! what an engine project. I know absolutely nothing about Harleys but any two cylinder, vee configured engine that turns 8000 has got to be interesting. I like your method to estimating the hp. Why not just run methanol instead of E98?Are you planning to run a carb or injection?
Rex
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Hi Rex,
We're going with a carb.
We're going ethanol for a number of reasons- we're in Illinois so it's available everywhere, it's easier on the parts, and e98 is pretty cheap. You get a little stoich advantage with methanol, but charge cooling (really important for an air cooled V engine)is better with corn squeeze so it's a wash IMO.
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I was wondering the same thing. But I don't even know enuf of what you're saying to doubt it.
So, I'll go along with your explanation. Keep us informed and after a month (year?) or two, I may be able to understand it.
I'm not being sarcastic. I know when someone knows a lot more than I do on a certain subject -- and after a while I get to know something I didn't know (or thought of) before. Keep us informed on your quest, please.
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No worries Stan. :-D
Just to make sure I checked using the calculators on Wallace's and got 239, So close enough. :cheers:
I'll keep everyone apprised as things get done . '24 is probably too aggressive a target especially figuring out a new fuel. 2025 definitely.
I'm sort of worried about what class this will fit in as the engine will not fit into an un-modified Sportster frame (too tall) so I have to raise the backbone. I'd also would really like a longer swingarm. I can keep the rest of it "stock".
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You can change the steering head angle, but you can't change the frame perimeter within the Modified class. The A-PF record is 195, so maybe try to cram it in there, or find a stock Harley frame it will fit into.
For power estimation, is there a drag class that is close to your specs? I'm not a Harley guy, but I think AHDRA has a 100" normally aspirated alcohol class. You could check their 1/4 mile trap speeds to see what's possible.
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I'm sort of worried about what class this will fit in as the engine will not fit into an un-modified Sportster frame (too tall) so I have to raise the backbone. I'd also would really like a longer swingarm. I can keep the rest of it "stock".
In modified you are allowed a 10% increase in wheelbase, so you can do a longer swingarm.
Make sure you have documentation listing the factory wheelbase.
As Sabat stated, if you raise the backbone you will be in "A" class, the good news to that is you would no longer be restrained on wheelbase.
Don
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I know there might have been discussion on this before.... but does the S&S engine meet the requirements of frame and engine from the same manufacturer...
You might want to get a written answer from the motorcycle chair for your log book. :cheers:
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You can change the steering head angle, but you can't change the frame perimeter within the Modified class. The A-PF record is 195, so maybe try to cram it in there, or find a stock Harley frame it will fit into.
For power estimation, is there a drag class that is close to your specs? I'm not a Harley guy, but I think AHDRA has a 100" normally aspirated alcohol class. You could check their 1/4 mile trap speeds to see what's possible.
Good to know. Yes AHDRA has the "Super Modified" Class 104 cid max, gas or alcohol. Talked to the sponsor so around 200 hp on alcohol, 160+mph in the 1/4 so with different gearing it's believable.
So, it does not have to be a Sportster frame? Just any stock Harley frame?
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I know there might have been discussion on this before.... but does the S&S engine meet the requirements of frame and engine from the same manufacturer...
You might want to get a written answer from the motorcycle chair for your log book. :cheers:
Motorcycle Chair? SCTA?
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The best start for building for Bonneville is get a rulebook and read it over and over. :cheers:
PM sent...
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The best start for building for Bonneville is get a rulebook and read it over and over. :cheers:
PM sent...
Awesome! Thank you!
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Forward facing air intake scoops are tricky with carbureted motorcycles. I tried a number of configurations and found that all produced a lean condition. Bigger jets did not improve the condition. It will take a lot of R & D to get that correct.
Joe
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I've tuned a many bike on my chassis dyno and the only twins I've seen in the 200 HP range has been the Ducatis. And their peak HP is at or above 11,000 RPM. Very recently, I tuned a extensively built S&S powered drag bike and it was in the 160 HP range. (can't remember the size, but IIRC is was bigger than 100" (1640 cc). To get toward that 200 HP, you will have to add something to the ethanol. :-D
BTW, I'm a big fan of E98 ....
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Forward facing air intake scoops are tricky with carbureted motorcycles. I tried a number of configurations and found that all produced a lean condition. Bigger jets did not improve the condition. It will take a lot of R & D to get that correct.
Joe
That's what I figured. I have some thoughts on why that occurs but I'll need to test those.
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.... Very recently, I tuned a extensively built S&S powered drag bike and it was in the 160 HP range. (can't remember the size, but IIRC is was bigger than 100" (1640 cc). To get toward that 200 HP, you will have to add something to the ethanol. :-D
BTW, I'm a big fan of E98 ....
Was that gas? Because that's what a number of HD drag bikes make on gas. Well, we'll see what she does. I think those calculators make a whole bunch of assumptions anyway. :|
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Yes that was gas ... C16 due to it's compression.
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Did bore measurements and it just fits into the 1650cc class. 4.002 with the bore honed. 1649.03cc swept displacement. Phew!!
New pistons: (3.997" nominal)
(https://i.imgur.com/jRokM0F.jpg)
(https://i.imgur.com/lz15eBK.jpg)
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1649.03? Yikes!! Don't forget to have the engine measured when it's as cold as can be! lol8 lol8
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1649.03? Yikes!! Don't forget to have the engine measured when it's as cold as can be! lol8 lol8
Amen to that! lol8
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Had a nice phone conversation with Derek. We'll be running in A class. So 193 mph and change. :?
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Short update:
Custom bearing cage design is complete. Machinist should have those done by 2/15.
Still have to order magneto, wires, trans gears and primary drive parts.
Decided to go with piston coolers, not so much that the pistons will need cooling with E98, but I'm concerned the cylinders might get oil starved at the piston speeds we'll be operating at.
Also, the rollers tend to slide around the crankpin oil holes at high rpm as there's too much oil there. The sliding makes for flat spots on the rollers and premature failure. To alleviate that, I'm machining slots fore and aft of the oil holes- about 1/8 long and .010 deep to encourage the oil to spread out away from the feed holes. That's a FAFO experiment. Seems to make sense though. We'll see how that works out.
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Short update:
Just got off the phone with Morris Magneto. Type F mag, custom advance cams, remote kill, and this will be the first one they've made with an electronic tachometer send. Should arrive in 4-6 weeks
Here's the partially machined cylinders. May drill the fins as they're pretty heavy at 18 lbs. Each. :-o
(https://i.imgur.com/7UPVJad.jpg)
(https://i.imgur.com/fLQGk3a.jpg)
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Weight is your friend at Bonneville....
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Weight is your friend at Bonneville....
Even high up on the frame? Wouldn't that make it harder to get out of a wobble?
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Magneto ordered. 26 degrees advance is what it'll provide, but I do have a choice as to where full advance kicks in. Anyone have degrees of spark advance numbers for alcohol fuels? Just need something to start with.
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Weight is your friend at Bonneville....
Even high up on the frame? Wouldn't that make it harder to get out of a wobble?
Balance the weight on the wheels within 5%. Most bikes that wobble have added a lot of weight to the rear wheel and end up with a light front. This bike had about 100lbs on the swingarm, 40 in the middle and 30 in the front to make it balance with the rider on. That silver on the top front is lead. You are not cornering, you are going straight on a low traction surface. This bike was mid 180s and ran arrow straight...
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This one tips the scales right at 800 lbs and a 50/50 weight split with the rider suited/saddled up. Also full suspension front and rear (and used it all with past and current conditions).
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Ross, nice shot of you sitting up to slow down after you 174mph run muutt
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Awesome! Thanks, gents. Undrilled it is then. ( don't think I'll need the ingot with this one)
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Rods and cages are complete. pics forthcoming.
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Regarding 8,000 rpm . . .
Many years ago, in an article about H-D dragsters, I read that a big unblown v-twin could not breathe well enough to achieve that engine speed. I wish you good luck with this project.
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Granted this is a small(er) Harley motor and is aided by a turbo, but it spins up pretty well (past 8000) in the lower gears. We were geared a bit too tall and needed more room to stretch out (short course only qualified) and hopefully get back to the 8k range. p.s. stock bottom end and rods, ebay pistons and borrowed heads.
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Regarding 8,000 rpm . . .
Many years ago, in an article about H-D dragsters, I read that a big unblown v-twin could not breathe well enough to achieve that engine speed. I wish you good luck with this project.
Thanks!
On nitromethane they can do 9k (for 10 seconds or so) but the stoich is like 1:1. That's one reason why we went with the M8 heads. Flow is like 375 CFM at 28", and that's more than I can stuff in the cylinders at 8k. The other is reduced valve inertia and corresponding spring pressure. The spring pressure on those drag engines is so high that with the plugs out you can't turn them over without a 4' breaker bar. :-o
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Here they are, Rods and big end cages
(https://i.imgur.com/d6XoZmH.jpg)
(https://i.imgur.com/KMF3Xp1.jpg)
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Granted this is a small(er) Harley motor and is aided by a turbo, but it spins up pretty well (past 8000) in the lower gears. We were geared a bit too tall and needed more room to stretch out (short course only qualified) and hopefully get back to the 8k range. p.s. stock bottom end and rods, ebay pistons and borrowed heads.
Cool! Who's heads?
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On another note, do you folks run an open velocity stack or is there enough stuff in the air that you'd recommend some kind of air filter?
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Coasted thru the timing traps after everything went quiet at 150 mph to find this (see attached). Well, being on an every expense spared budget, I reached out and borrowed a set of heads, stockers, from a "no kill shelter" for used motorcycle parts. You can still smell the questionable/criminal past. Nothing special, just cheap (free) and available.
Edit 1). Cheap (free) and available sounds like one of my ex's. She said she was "fast". I thought "racer". Nope, she just drank alot and put out on the first date.
Edit 2). Trying to make old parts go fast is about as hard as making fast parts get old so I always opt for the least expensive parts. YMMV.
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Coasted thru the timing traps after everything went quiet at 150 mph to find this (see attached). Well, being on an every expense spared budget, I reached out and borrowed a set of heads, stockers, from a "no kill shelter" for used motorcycle parts. You can still smell the questionable/criminal past. Nothing special, just cheap (free) and available.
EEK! :?
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Trying to make old parts go fast is about as hard as making fast parts get old
LOL. That a great line!
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delcrossv,
Back in 2013 I was "smart" enough to buy a new copy of Kevin Cameron's book
"Classic Motorcycle Race Engines" fantastic book! and one that I find myself reading again and again which now is one of those occasions (I think it is the 4th or 5th time) and I came across some information of the causes of roller bearing "skidding" which may be of interest to you. According to Kevin the instantaneous rpm of a roller rod bearing changes by 25% twice each revolution of the crank revolution and it is the acceleration, +and-, of the bearing that causes the skidding. The major way of increasing the rpm that this occurs at is to minimize the inertia of the rollers and cage. I am sure that you have made every effort to minimize the weight of your bearings but 8000 rpm with a 4 inch stroke may be a challenge. Kevin also does an analysis of the Harley XR750 engine and that they were raced at 9000-9500 rpm but they had a 3 inch stroke also and they made 110+ HP also.
Keep up the great work and keep the updates coming.
Rex
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delcrossv,
Back in 2013 I was "smart" enough to buy a new copy of Kevin Cameron's book
"Classic Motorcycle Race Engines" fantastic book! and one that I find myself reading again and again which now is one of those occasions (I think it is the 4th or 5th time) and I came across some information of the causes of roller bearing "skidding" which may be of interest to you. According to Kevin the instantaneous rpm of a roller rod bearing changes by 25% twice each revolution of the crank revolution and it is the acceleration, +and-, of the bearing that causes the skidding. The major way of increasing the rpm that this occurs at is to minimize the inertia of the rollers and cage. I am sure that you have made every effort to minimize the weight of your bearings but 8000 rpm with a 4 inch stroke may be a challenge. Kevin also does an analysis of the Harley XR750 engine and that they were raced at 9000-9500 rpm but they had a 3 inch stroke also and they made 110+ HP also.
Keep up the great work and keep the updates coming.
Rex
Thanks Rex, very interesting and does make sense. We went with Al cages, instead of bronze and a larger crankpin. Unless we tried something exotic, we're stuck with steel rollers. If it becomes an issue, I do recall Carrillo did make plain big end rods for someone, that may be something to try down the road.
Pretty bizarre:
(https://i.imgur.com/djToBUU.jpg)
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Cylinders are cut for pushrods so did a quick mockup
(https://i.imgur.com/YEBVrps.jpg)
(https://i.imgur.com/h0ulZxh.jpg)