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Discussion Starter #1
Here I am, BACK to ask the most knowledgeable racers in the land (YB'ers) a question and I know that I'll get answers that will lead me in the right direction. SO HERE GOES!!!

I've been building and as of late, testing a newly built BBC procharged combination that uses a Rossler XHD-210 (3-speed, 2.10 first geared) tranny. The car has a 4.30 rear gear in it as of right now. This is a Full chassis Big Tired car. I am still in the testing phase of this combo but it has shown SOME promise but still has a ways to go.

My problem is that I *THINK* that I need different gearing in the car, but I am unfamiliar of what kind of gearing that a supercharged combo needs. I've but my question to different local racers and they all say that a supercharged car needs to feel "LOADED" more than a Nitrous car does. That a supercharged car will not "like" as much gear. This is a vid of my last "TAPED" run with the combo:
http://www.youtube.com/watch?v=jyI3xDaPXpI
Not much has changed as far as where the car is going to drive gear on the track. This is an eighth-mile track and the car is not shifting to drive gear until about 150-100 feet before the finish line. I feel that I am leaving a lot of E.T. on the table here. The car also seems to be sort of "LAYING DOWN" in the middle of the runs, as I LOOK at it on video.

What is surprising though is that the car is running a really good 60-ft time, but then after that only a decent 330 and then only a decent 1/8th mile time and a dissapointing MPH for the elapsed time. Everything else (looking at the data) seems to be fine. My friends that are familiar with the combo all seem to think that the car needs more gearing and that would let the combo use more of the tranny during the run. They are saying that the combo needs to be going into drive gear by the 330ft mark. I am worried that gearing the car to achieve this would really start blowing away the tires. The car is already running high 1.0's to 1.12 60-ft times on a very consistent basis with the setup as is.
Can this combo use more GEAR in the REAR, or does it have a different problem??

Okay you PROCHARGER / SUPERCHARGER GURU's ......................
ANY SUGGESTIONS ???? (HELP!!)
 

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MFI on CH3OH
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What is the rpm drop on the shift ? Remember that boost is directly related to engine RPM's. Without knowing all the specs maybe a looser convertor and more rear gear would help as you can hear the RPM dip and stay lower in the video after 1st gear. I would be aiming to be in top gear at max rpms across the line

I might be wrong, im sure someone will help you out as i dont do any 1/8th mile racing .
 

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Discussion Starter #5
The car has Mickey Thompson 33 x 16.5 x 15's .
 

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Discussion Starter #6
What is the rpm drop on the shift ? Remember that boost is directly related to engine RPM's. Without knowing all the specs maybe a looser convertor and more rear gear would help as you can hear the RPM dip and stay lower in the video after 1st gear. I would be aiming to be in top gear at max rpms across the line

I might be wrong, im sure someone will help you out as i dont do any 1/8th mile racing .
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I have been launching the car at 5000 RPMs and at that rpm it is making about 13.5 lbs of boost. *I do believe it can leave with MORE BOOST and still launch reliably*. At 5200 it is making 15.5lbs of boost, and at 5600rpms it is making 17.4lbs of Boost, 6000rpms making 20.6lbs and 6250rpms it's making 24.0lbs. At 7000 rpms it shows to be making 29.0 lbs of boost. it falls from it's 7800 rpm shift point down to about 6700-6800 rpms during a run.
It shifts into drive (third) gear at about 100-150 ft before the finish stripe of the 1/8th mile. The data recorder of the FAST EFI system records engine rpm and on all of the runs it is saying that the engine rpms are dropping 1000-1100RPMs on each of the shifts.
Initially, before I ever ran the car, I was thinking that this 4.30 geared, 2650 lb car with the 2.10 first gear trans would need to have the rear gearing reduced numerically to make it through the 1/8th mile course. But after installing everything it is running the entire eighth mile and only using two gears fully and very little of the third and it would seem that I may need to INCREASE the gear (numerically) to allow all of the tranny's gearing to be effectively used.

This is my first supercharged combo, so I have a questions.

With my current convertor is the 1100rpm drop is too much and the convertor needs to be loosened to compensate?
Could the 1100rpm drop between each gear shift on this procharged application be causing the lag during the entire run, enough to drag it down so that it's only using two gear ranges of the transmission and only a small part of the third?
Or is this just a problem of not enough rear gearing?
 

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MFI on CH3OH
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1100rpm isnt to bad, i think like you said you need to put some different gears in it so you can use all three speeds effectively. As to what gear to go to, maybe 4.8's or more.

Thats only a guesstimate, as i said before there is some experienced 1/8th mile guys who will chime in soon with a more concrete answer.
 

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Procharged SBC Enthusiast
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I would wonder if you would not have such a big fall off between shifts if your manifold was smaller and you went to a single throttle body. Seems that if you are running primarily 1/8 mile that your engine would be more responsive through the shifts with less manifold and the throttle body be a single open istead of dual 4 hole throttle bodys .
 

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Discussion Starter #9
I would wonder if you would not have such a big fall off between shifts if your manifold was smaller and you went to a single throttle body. Seems that if you are running primarily 1/8 mile that your engine would be more responsive through the shifts with less manifold and the throttle body be a single open istead of dual 4 hole throttle bodys .

That's one thing that I need to know.
On the shifts (of a Procharged Race Combo), is 1100 - 1000 rpm drop a LARGE DROP or is this about the norm? This is my first supercharged project but on my other cars this would not have been a bad drop of rpms on the shift.
I don't know, so that's why I am asking! Just trying to troubleshoot this deal.
 

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I run small blocks so I cant tell you specifically what is normal drop on a BBC . But seeing that you are fuel injected all space above the injectors is of no benefit. When you shift and you have rpm drop the supercharger also has rpm drop which in turn pushes less air. You have alot of extra intake volume that the supercharger has to fill . On your shifts I would have to assume that it would recover quicker from the drop with less intake manifold and a single throttle body. JMOP
 

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Procharger Power
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What size engine? You do need more gear if you are only racing 1/8th mile. The RPM drop on the shift is ok as it would indicate a tight converter.
 

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Discussion Starter #12
What size engine? You do need more gear if you are only racing 1/8th mile. The RPM drop on the shift is ok as it would indicate a tight converter.

Yes, I am only trying to race 1/8th mile with this car. 498 ci
 

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I would think since you have a big tire car, and its not super light and are only running 1/8th mile you should be able to use a lower gear in the rear and this will allow you to have a lower overall ratio in second to accelerate the car and also allow you to get out of first earlier without the fear of excessive rpm drop as it shifts into second. This will make the car pull harder in second and if you have trouble with excessive wheelspeed on launch you can always pull a little timing to calm it down.

It may be me but it sounds like it is running a little high on rpm to avoid the shift into 2nd and then after it hits second its kind of gagging, by having the overall 2nd gear ratio lower it will not be working nearly as hard and will be able to build rpm and boost faster.

I don’t know if you have dyno sheets on the car but if you do you will be able to determine how far you are from peak torque at the shift and for how long and make an educated guess about the converter. After you get the car worked out with the new gearing and get the timing and fuel maps just where you want them to make sure you are not leaving anything on the table then maybe you may want to loosen the converter but to do it before the gearing is optimized first so you have a better idea of what you want to do, I feel would be a mistake.

You might want to contact Rick Fleck (Flex) and see if he is tight lipped as he has a lot of experience going fast in the 1/8th with a procharger and BBC.
 

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Discussion Starter #15
I would think since you have a big tire car, and its not super light and are only running 1/8th mile you should be able to use a lower gear in the rear and this will allow you to have a lower overall ratio in second to accelerate the car and also allow you to get out of first earlier without the fear of excessive rpm drop as it shifts into second. This will make the car pull harder in second and if you have trouble with excessive wheelspeed on launch you can always pull a little timing to calm it down.

It may be me but it sounds like it is running a little high on rpm to avoid the shift into 2nd and then after it hits second its kind of gagging, by having the overall 2nd gear ratio lower it will not be working nearly as hard and will be able to build rpm and boost faster.

I don’t know if you have dyno sheets on the car but if you do you will be able to determine how far you are from peak torque at the shift and for how long and make an educated guess about the converter. After you get the car worked out with the new gearing and get the timing and fuel maps just where you want them to make sure you are not leaving anything on the table then maybe you may want to loosen the converter but to do it before the gearing is optimized first so you have a better idea of what you want to do, I feel would be a mistake.

You might want to contact Rick Fleck (Flex) and see if he is tight lipped as he has a lot of experience going fast in the 1/8th with a procharger and BBC.
*FIRST*
THANK YOU to EVERYONE that has responded.

Thank You "bottlefed1" also for this answer. It really kind of goes along with what the local guys have been telling me on this problem. Just throwing it out there, but what THEY have been telling me is to gear-up (numerically) the rear end one or two steps from the 4.30 that is in it now and Hammer on it. If it's hazing the tires or something else foul on the leave then shave off some timing until I am leaving/launching with only about 1/2 revolution on the rear slicks at the hit. Then they are saying since it is a big tire car I can probably put the timing all back in about a second or so. Then they pretty much agree with you in that the added gearing would carry the car through the rest of the run assuming everything else is correct with the tuneup.

Now I DO have one local guy that looked at the video and says that the car needs one step up in gearing AND he thinks that it is running like a supercharged car that is DOWN on timing, INCLUDING the LAUNCH! I'm not really sure about THAT theory though:) . He also thinks that I need to launch under more boost pressure. He thinks that what I am producing at the launch rpm is not enough and combined with not having enough rear gearing that I am lugging the car down from the start. HUH???
 

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who done the cam? what was different in the tune up on the 2`nd pass. 1`st pass no candles- 2`nd pass candles.
 

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Discussion Starter #17
who done the cam? what was different in the tune up on the 2`nd pass. 1`st pass no candles- 2`nd pass candles.

ERIC STUBBS of Eric Stubbs Racing did the tuning. He's great on that kind of stuff and I could really recommend him. from the first pass to the second all Eric did here was make some adjustments to the fuel curve.

Now the camshaft? That's one area that I already KNOW can and WILL need improvement. I wanna use STEVE for one of his camshafts that he can tailor to my specific application.

I have a lot of room for improvement on this thing. the right camshaft, it seems obviously more rear-gearing, better headers.
It seems to be running good though at the hit, if a 2650 lb car can generate consistent high 1.0 60-fts, but seems to not be using its full potential the rest of the way through.
 

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ERIC STUBBS of Eric Stubbs Racing did the tuning. He's great on that kind of stuff and I could really recommend him. from the first pass to the second all Eric did here was make some adjustments to the fuel curve.

Now the camshaft? That's one area that I already KNOW can and WILL need improvement. I wanna use STEVE for one of his camshafts that he can tailor to my specific application.

I have a lot of room for improvement on this thing. the right camshaft, it seems obviously more rear-gearing, better headers.
It seems to be running good though at the hit, if a 2650 lb car can generate consistent high 1.0 60-fts, but seems to not be using its full potential the rest of the way through.
the reason i ask about the cam is maybe your blowing to much out of the exhaust . some should be helpful controlling the temp. of the exhaust valve. could this be playing into the sluggish acceleration rate? as for the big intake, i would pm. ron clevenger on yb and ask him somethings before i removed it. really super nice car. i`m on board with getting morris to spec a cam and compare to what you have. just a side note my buddy with a 598 bbf c-heads f3r went to the dyno with a .9 in. cam and broke the whole jesel set on 1 side . it was a nitrous cam. he just got a new one.lol
 

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Discussion Starter #19
Been giving serious consideration to ordering a 4.71 and seeing how that does with my prob. :confused::confused:
 

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Also something i noticed on this car when i have seen it run is it blows fire out of the exhaust during the burnout and somtimes during the run. I dont know if this is a concern or not, but i have never seen a car with this type of engine combo do that. I have only seen nitrous cars seem to do this. I may be way off but it seems odd to me, i know Eric knows his stuff it is just something i noticed and thought HMMM thats different!! just my 2 cents Tony whats up man, Bryan Vance.
 
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