Landracing Forum
Tech Information => Technical Discussion => Topic started by: Dave Haller on August 24, 2008, 12:48:03 PM
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I'm in a bit of a delema. I have a 481 inch BBC, running a Ron's Terminator Injection system hooked up to a Turbo 400 that has been beefed up. I ran with no problems at Speedweek 08. The engine came on strong in first gear, 2.48, second gear 1.48, then dropped to 4700 rpm in third, 1 to 1, and lugged to the best of 5900 in that gear. I kept changing out the rear end gears ending up with a 2.47 and speed of 213 which is way low for what I was trying to do. Shift points in 1st and 2nd were 7500 rpm. I'm running methanol for fuel, compression in the engine is about 13:1. Tires are the M/T 30", fronts are Goodyears 23". I know my scoop is way to big and the engine compartment is open. Any suggestions on horsepower needs, transmission gearing, transmission recomendations. I know Danny Boy shifts quickly with a Liberty trans with minimum rpm drop between 3rd and fourth as well as fifth. Any help is much appreciated,
Thanks,
Dave Haller #93 A/FL
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Dave, I love my Liberty. You can get any gear ratio you want.
Mine is
2.50 first,
1.50 second
1.25 third.
1.10 forth
1.00 fifth.
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Doug,
That is what I am considering. Do your ratios keep the rpm's up in the power band between shifts? I have some numbers worked out and they are close to yours.
Thanks,
Dave Haller
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Dave we are running a G-Force with 1.923-1st, 1.331-2nd, 1.000-3rd, and 0.931 4th. 4th is actually the 3rd gear cluster and you can pick lots of different overdrive ratios for it and you run the 1 to 1 fourth as 3rd. We only drop about 500 rpm on the 3-4 shift this way.
For the speeds you hope to run I would look at their 5 speed, GF-5R, as you could then run the 5th 1 to 1 as 3rd (check with them) and run 3rd and 4th as overdrive gears to keep the rpm drop at the top end low with close ratios.
http://www.gforcetransmissions.com/tran_gf5r.asp
For instance with that transmission you could run a high 1st like we do of 2.00. We still can't use more than 50% throttle in 1st with the added weight, so I don't see where a lower gear would help as we would then probably spin the tires easier.
http://www.gforcetransmissions.com/pdfs/GF5r_ratio.pdf
2nd could be a 1.38 and then the 5th would give you a 3rd of 1 to 1.
The 3rd gear set then could be like a .87 and the 4th gear set could be as high as .776 if needed.
Those are just numbers I picked at random. You need to be realistic about the cars top speed and then use my "RPM in gears for 5 Speed Car Transmission" spreadsheet....
http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html
.............. and plug in different gear combinations and look at different rpm shift points and look at the rpm drop after the shift so you pick ratios that keep you in the power band. All of that is right there and easy to see with the spreadsheet. The first couple rpm drops can be large and will help to keep from over powering the tires, but the last need to be very close.
Missed meeting you on the salt,
Sum
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Dave, I have mine so the last shift 4-5 drops 10%. If you are shifting at 7000 it will drop to 6300. I have a quick change with a 2.3 ring and pinion. I just looked up my gear chart and I missed the ratios a little. The real ratios are
First 2.17
Second 1.52
Third 1.27
Forth 1.10
Fifth 1.00
I have a real nice spread sheet that someone sent to me and I forgot who. I can email it to you if you have excell and you can work out what gears you need.
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Dave,
Have you had the motor on the dyno? If so what were the results? When you say you changed gears what gear did you start with and what was the rpm you were running with that gear? If your motor is not up to par it does not matter what transmission you run.
Tom G.
PS. Post a picture of your car.
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Tom G.
I didn't dyno the engine. I have a friend up here that has a chassis dyno but the car is set up with a direct drive, no torque converter so putting it on his dyno was not an option. The estimated horsepower is close to 900 based on the engine builders stats. It does come on very strong in first and second buzzing to 7500 with no problem. I think keeping it up in the rpm power range is the answer as well as using a smaller opening on the scoop and enclosing the rest of the car.
Dave H.
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Dave,
IMO do yourself a big favor and put your motor on the dyno, and see where the peak torque and HP are. Then you can see what exactly your RPM range for making power is and not be guessing. It will be way cheaper than buying a $5000 transmission especially if you don't need it. Remember that motors will aways pull good in 1st and 2nd as you don't have the drag that you encounter until high gear.
I helped a friend run his lakester back in the mid to late 1980's at El Mirage. It was a real budget car, old rear engine dragster, no covering of the motor, headers stuck well into the breeze, front of the car was covered but no covering of the roll cage and no wind deflector. With a basically stock 327, with a 3/4 grind cam in it, we were able to run a best of 178 at El Mirage on the 1.3 mile course. (if this car had 300 honest HP I would be amazed) For a transmission it had just a two speed lenco with a 1.44 first gear, and as I recall we had 3.08 gears in the rear. The car was driven off the line not pushed.
When I bought the 300 Street Roadster the motor had been blown up at the last meet of the season at El Mirage. I scrounged up some junk parts just to be able to run the car. The motor parts I found were a 350 with 10-1 pistons, cast crank, stock cast pressed pin rods, two bolt main block, stock oil pan and pump, Comp Cams 280 degree hydraulic cam, Early Corvette heads era 1965 with stamped Chevy rockers, the only parts I was able to use off the blown up motor was the single 4 barrel intake manifold with the 650 Holley, and the MSD crank trigger and distributor. Transmission was a turbo 350 that has special kilgore gears in it that are 2.42-1 in first, and 1.42-1 in second. Rear end is a speedway mini quickchange. This car ran a best of 163 mph with that motor at El Mirage, with a 6000 RPM chip in the MSD unit and 2.95 rear end gears. We would go through the lights around 5700 RPM, just where the cam was peaking.
If I had a 900HP motor in my street roadster it would go around 210+ at Bonneville. I am not trying to tell you what to do, only trying to help. Good luck with whatever you do.
Tom G.
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Speaking of running good in first and second gear -- our first run at Bonneville this year we set what I believe to be a record. Past the 1 with our internal injector cover on. Ran pretty good in 1st and 2nd -- just wouldn't pull in third.
Stan Back
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Tom G,
Can you email me at my home? dhhaller@comcast.net. I would like to share and receive more info on my set up and don't want to tie up this chat room with stupid questions. I have lots to share.
Thanks,
Dave Haller
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Dave, I use a Tex T-101, very similar to the G-Force. 1.60 1st, 1.23 2nd, 1.00 3rd, & .96 4th. Tex can assemble any 4-speed trans you want with pristine used Nascar gears and used aluminum cases. Their T101A is tricker but not really necessary. I just purchased a 2nd one off E-Bay for $1000.00; a little different gearing but still with an .945 OD.
Mine are both clutchless but we still use it in the first 2 shifts. Last one we just yank it. Gearing changes ment dissasembly of the trans but gear sets were only $75.00. I believe Bob Brissete uses a similar trans in his lakester. As these NASCAR suppliers change to the "newest and best" the older equipment is pretty reasonable and for what I have found bullet proof for us. There are more of the OD and very close ratio transmissions on the salt than you can imagine...Good Luck ..JD
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JD,
Do you have the contact info for Tex T-101? Looking to change trans combo next year.
Tom
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www.texracing.com was how I did it after talking to Keith Turk. Everything you need to see is on the net. I had them send me a complete gearing chart for the T-101 and I made my choices from that. Did it all over the phone. Because of the lack of room I had to use a Hurst shifter but would have preferred the Long but it would not fit.
It came with an oil spray bar but I did not get a pump or reservoir; same reason lack of room. They "appear" the same as a Muncie or BW-T10 in demensions but they are massively strong. I had to make a custon cradle to fit my floor jack to put it in. I weighs in at a little over 100#. They are a "work of art" inside. Good Luck.............I now carry an extra
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Thanks JD,
I'll check it out.
Tom
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Tom G.
Emailed you last night but got an error message back. Sent it again this morning. Let me know if you got it,
Thanks,
Dave Haller
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Tom --
I used to have shifting problems with my Super T10 (?) and I believe it was Tex Racing that rebuilt and/or modified my Hurst shifter. Apparently the $99 Indy shifter mechaniism and the more expensive models are basically the same. I had them "tune it up" with their own rods and levers and haven't had a problem since. And I didn't pay for the reverse set-up they offer and saved a few bucks. You might talk to them about the shifters, too.
Stan
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Tom G.
Emailed you last night but got an error message back. Sent it again this morning. Let me know if you got it,
Thanks,
Dave Haller
Dave,
Got your email last night and the one you sent this morning. Just replied with an email.
Tom G.
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Dave,
I ran some numbers using your ratios and several things that you might think about. At 7500 rpm in second you should be going around 182 mph so when you shift into high the engine should pull down to 5050 rpm and you said it goes down to 4700 rpm, this may be simply the speed at which the 400 shifts. It takes so long that the car actually slows down before top gear is engaged. You might also think about turning the engine tighter in second gear, if you went to 8000 rpm your engine should then be at 5400 in top gear and maybe this is closer to your max torque range and the engine will continue to pull. A good big block should easily be able to go 8000 even 8500 in second. At 8500 you would be going 206 mph and the engine would pull down to 5750 rpm going into top gear.
As Doug and Sum say the real solution is more and closer ratios. The general rule of thumb on picking ratios is that each step should be about 1/2 of the previous step. Look at Doug's ratios, the difference is .55 first to second, .25 second to third, .17 third to forth and .1 forth to fifth. Very good selection, it mostly has to do with aero drag being a square function.
Rex
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I have driven a AT 400 with 30" and 2.47s---ran 267. with a 509---I would advise what several have recomended---put it on a DYno and work with a BOAT eng. builder!!!!!!!!!!!
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Okay guys, I'm starting to see the light here. I will put the engine on a dyno. There are a couple available up this way. Once I do that I have arranged to have more work done on the engine if needed. The transmission change will have to happen. I am looking at racingjunk.com and see several options out there. Like most of you I am on my own dime on this thing so I need to be frugal but understand the need for bulletproof parts to survive. Thanks for all the suggestions and help. Listening to the very fast ones out there you can hear the rpm drop in higher gears and it isn't much.
Dave Haller
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-x
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I'm in a bit of a delema. I have a 481 inch BBC, running a Ron's Terminator Injection system hooked up to a Turbo 400 that has been beefed up. I ran with no problems at Speedweek 08. The engine came on strong in first gear, 2.48, second gear 1.48, then dropped to 4700 rpm in third, 1 to 1, and lugged to the best of 5900 in that gear. I kept changing out the rear end gears ending up with a 2.47 and speed of 213 which is way low for what I was trying to do. Shift points in 1st and 2nd were 7500 rpm. I'm running methanol for fuel, compression in the engine is about 13:1. Tires are the M/T 30", fronts are Goodyears 23". I know my scoop is way to big and the engine compartment is open. Any suggestions on horsepower needs, transmission gearing, transmission recomendations. I know Danny Boy shifts quickly with a Liberty trans with minimum rpm drop between 3rd and fourth as well as fifth. Any help is much appreciated,
Thanks,
Dave Haller #93 A/FL
Dave
It sounds more like a tuning problem to me. Unless your lakester is carrying tons of weight, what does it weight?
I know Bob Joenck use to run high gear only in his roadsters and ran a lot faster than that on gas.
JL222
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I have driven a AT 400 with 30" and 2.47s---ran 267. with a 509---I would advise what several have recomended---put it on a DYno and work with a BOAT eng. builder!!!!!!!!!!!
Congratulations Sparky 300 + NA what an accomplishment!
On your 267 run my program calculates about 7800 using 247s -30" tires with no growth 13 ft frontal area and .5 cd [guessing on fa and cd] and shows 1110 hp to go that fast. If i knew the actual hp numbers and frontal areas i could get closer numbers on cd, but thats the numbers I needed to input to get that speed.
If i knew your 300 mph hp and frontal area? But you might want to keep your speed secreats
JL222
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with the 2.47we were turning about 7300---at 269.--Dave the AT 400 is a good choice in my opinion---shift at 8 it comes back into the high 5's
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We have a real soft shift set up almost stock---we do not want to shock the tires---the eng pulls down, the trans slips some and the tires spin a little---we usually lock up again at arount 57-5800 with the 400---this meet I was running a 2 speed PG---shiffed at 8000---pulle down to 43-4400 after shift---thinking of raising that to 8200 trying to get 2 runs over 300.---do not know what my frontal or CD is---sorry
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My car worked fine on a chassis dyno with a PG and no convertor. Turbo has way more gear in low so should start rollers easily. I was short shifting because of tire spin and pulling the engine to 4000rpm but still ran 237 to the 1/4. In a perfect world a 4 or 5 speed may be ideal, but if you don't have aero and traction, with a ample dose of H.P.what does it matter? Sparky's PG equipped lakester @ 300mph says it all.
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..........Sparky's PG equipped lakester @ 300mph says it all.........
He also has a gear vendors in there also, but i'm not sure exactly how he was going through the gears this year even though I think he told me :cry:,
Sum
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Great accomplishment Sparky. I have some minor observation to make in the class you are running. Your record, lucky set at the end of the week, took one set earlier in the meet by Seth. (Oh-O) If I were you I would be at the WF first in line and get your 2-300's set quick; if you blink the record might be a bunch over the 299. I'm sure Seth and crew will be coming after ALL the lakester records he has the set with the earlier car and lost.
Knock-um dead Spark and get that Blue Hat..........JD
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JD---I know that you seeing it the same way as I do---I know that my time is most likely very well limited---I just had slightly less new car Problems than Seth---I have been "Highly motivated" since I heard what Heads he ordered!!!!!!!!when he first started the car---I am going to be spotting him 2-300 hp --- my dumb Home Depot biginers luck will not luck out forver!!!!!!!
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Dave, as said before get the motor dyno'd, once you have a hp number you can figure a pretty accurate cd number for your car. As others have been saying you 'should' be able to run faster and probably can with the HP you have now. once you have your aero data you can plot a curve of speed vs hp for your car. Then you can overlay a plot of your rpm and HP over that plot and you see exactly WHAT rpm you need at a given speed in order to beat the aero drag. Keep that HP on the left side of the drag line! With a little math you can insure the new tranny ratios you are proposing will have enough margin. There is some very good advice on percent drop with each next gear, this alone will get you pretty much where you need to be but having some hard numbers...even if it's hard to get them right on, you will be close. Use the speed and rpm you hit the wall with the coinciding HP you will find at the dyno and your off to the races....but as always..racing on paper is much easier...and your results will vary..but hopefully in a positive direction...geting the right HP and driveline combo is half the fun, it has taken us 4 years or so trying to get a record on our GMR with a big block..finally got the A in August...that damn Murphy guy is an asswipe.
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"The general rule of thumb on picking ratios is that each step should be about 1/2 of the previous step. Look at Doug's ratios, the difference is .55 first to second, .25 second to third, .17 third to forth and .1 forth to fifth. Very good selection, it mostly has to do with aero drag being a square function"
Way, way more complicated than that.
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I approach the problem similar to Hans---except I use the DYNO TQ #s X FDR-final drive ratio X TR--Trans ratio X RA- rear axel ratio X TC -tire correction--= TE Tractive effort---
go for the biggest number you can put down at the speed you are trying to run
PS dont forget: TQ, TR, RA and TC and, AND RPM are all almost equal factors
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Sorry for being so verbose---if you can't pull the speed: then you have to decrease aero drag or parasitic losses or add more TE
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Sparky and others,
Engine is going on the dyno in about two weeks or so. Aero is being addressed today, the 14th, by some folks up this way that can help. Should have a much better idea how to make it go faster after all this great direction from all of you hot rodders. Sparky, are you going to the World Finals if the weather holds? I will probably come down to help a friend with his bike and talk with some of you about options on my ride and take lots of pictures for more ideas.
Dave Haller
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I am going to WOS---doubt if WF---I am taking JD's advice---go sOOn
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CORRECTION:
FDR= TR x RA
Overall Ratio = FDR x TC
TE=TQ x OR
Sorry for the confusion
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I ran into an aero wall at my torque peak at the 4 mile mark will need to do some work to catch you fast guys
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these formulas lets one play with appricots and apples---remember there is more than one way to skin a cat!!!!!!!!!!!!!!!
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Dave, Many years ago I did some testing on the dyno before they had the computerized ones they have now. My findings then was the engine accelerated the quickest between the torque peak and the horsepower peak. Now this was done with a stop watch and a constant load on the dyno that would let the engine run about 500 rpm over its peak horsepower. I have always tired to gear my engines to run in this area on oval and road race tracks. In LSR racing because of the high aero forces that increase at the square of the speed increase we don't have a constant load so that approach might not work so good.
Anyone please, jump in here and give me a better way if you have found one.
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As Mr. Schimmer cleverly points out later, this post contained "Lots of buzz words not much sense", so I've removed it as a courtesy to small children who may be injured by reading it.
If you must, he has also carefully over-written my control of my own thoughts by re-printing something that he insists is worthless - to what purpose, I'll let the readers decide.
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...........Unless a large number of gears can be used, this means compromising the 1st gear (reducing the number; e.g., 2.00 instead of 2.50:1) to close up the intermediate ratios since the engine is only pulling weight (not as much aero) in 1st gear and can afford less torque multiplication..............
I agree, if you have any HP the high first won't hurt you on the salt with the limited traction. We run a 1.90 first and still over-power the tires with anything over about 50% throttle now and that is with a 5000 lb. car weight with about 1/2 of that on the rear. Even the 1.33 second can produce wheel spin and requires less than 100% throttle. Since we haven't reached the point of achieving traction with 100% throttle in 1st and 2nd I don't believe that the increased weight in the car has hurt acceleration and has probably helped it.
c ya,
Sum
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Ran the engine on the dyno yesterday with surprising results. It was way fat on the pill I ran at speedweek. Found a clogged jet, two aimed wrong, fixed all that, had an ignition problem, fixed that and made several pulls. Torque is consistant between 4000 rpm and 7000 rpm dropping slightly between 7000 and 7500. Really like that. Rings started going away and stopped the dyno. Will freshen it up and take it back to get the fuel curve right. Great time, very happy with the numbers. Plan on enclosing the rest of the body this winter, get the tune right and be back in August, hopefully to go really fast.
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So whats the bottom line Dave, how many ponies?
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Well, the best hp run was fat and still cold with 604 torque and 760 horse. Got much more coming with fresh rings, re-jetting, relief valve setting and heat in the engine.
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Panic said:
"the engine accelerated the quickest between the torque peak and the horsepower peak"
AFAIK thats a safe assumption with few exceptions.
However, what remains is "what percentage of the RPM range does this span?", which is (under ideal circumstances) the range to which engine speed should recover on every gear change.
As the maximum speed goes up, the necessity for compliance on the final shift into high gear becomes critical, and with speeds over 200 (?) even the penultimate gears become highly important since the car is accelerating against a huge aero load and falling below the power curve pretty much writes off the run (unless the chassis is traction rather than power limited).
Unless a large number of gears can be used, this means compromising the 1st gear (reducing the number; e.g., 2.00 instead of 2.50:1) to close up the intermediate ratios since the engine is only pulling weight (not as much aero) in 1st gear and can afford less torque multiplication.
A bike engine might have 12 or 14,000 RPM to play with, but only serious power in the last 20% or less; a diesel or high pressure turbo typically has a much wider power range.
In summary: all transmissions have some degree of progression towards the final ratio. The slope of the change in RPM drop is greatly affected by top speed, and the same drop between successive ratios that works well for 200 Mph may abort a 250 Mph run when the engine falls off the planet on the 3-4 shift.
The only nice thing about planning LSR ratios is that (in general) the progression can be a clean slope with no spikes or glitches as would be common in gear sets planned for road race courses to accommodate specific shift points and track lengths."
Lots of buzz words not much sense.
Rex
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Transmission ratios become more important when engine power bans get narrow. The narrower the power ban the closer the ratios need to be, especially the last shift. If the spread between the last two gears drops the engine to a point that the engine is not generating enough horse power to overcome the aero load at that speed you will not go faster, again this is assuming that you have some idea of what the aero load is at your target top speed and that your engine is sufficiently powerful enough to attain that speed. When using big engines like Dave has with very broad power bans transmissions like TH400s and Powerglides can be used because when the last shift is made the engine is not brought down below the power required to maintain the shift speed. Looking at the additional information that Dave is providing it looks like his problems are more engine related than transmission related and once he gets the engine happy it will probably pull right thru once in high gear (again assuming that his final ratio is not to optimistic).
I have seen a number of cars set records using high gear only, they were on the long course, had good torque producing enginies and had pretty good push trucks but it can be done without a trans. I have related this story several times but back in 02 or 03 the no. 302 roadster, runs XXO/FR has a strong GMC six and likes nitro set their record at around 204-5 and broke the trans, but they wanted their dad to make a run so they took the guts out of the tranny, locked it in high gear and pushed him off, it grunted and groaned but ended up reseting the record at 208, high gear only.
This isn't a dark science, it is knowing the engine power curve, the loads that the car will see at the desired speed, aero and rolling, and then establishing the ratios starting from the top gear going backwards.
Rex
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Rex,
Thanks very much for that input, I will put it to good use. Getting the engine freshened up, will dyno again then figure out the rest as you suggest.
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Rex, That was me (JD) in 2003 in our #292 XXO/FR. My son set the record in 02 at 202. On my first run in 03 I took out the drive gear on the cluster. Back in the pits we took out the cluster over filled it with tranny oil and I qualified at 2005. I left the truck to early and blubbered it a lot until I figured out how much to give it. Did better the next morning, still left the truck to early but knew how to drive it better and went 215 in the last mile. In 02 we had 30" tires, in 03 I had 32" tires, both of use use a 2.56 rear gear. It was the 72% nitro that made it all happen. High gear only was used a lot in the 50's and 60's especially on a load.
In 04 we came back with the Tex OD trans and lost the cylinder head after we qualified at 211.
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Jimmy,
Thanks for filling in the details, didn't mean to give the credit to the wrong people. I just remember being there and seeing it and being really impressed! 72% in the tank!! man those GMCs like their "soda pop"!!! Nothing like "the can", high gear only and a good push truck!!
Jimmy, thanks again and also for the great show in 02.
Rex