Guest Tom Scala Posted July 12, 2002 Share Posted July 12, 2002 I just bought a hybrid t3/t40e,50 trim,with a stock .63 a/r turbine mounted on it. It will be replacing another hybrid with a Buick GN compressor on a stock turbine. At the track with SDS,420cc injectors, a Spearco,2.5" exhaust with Super Turbo muffler & running 15 psi it went a best of 13.88 @ 99+,2.17 60' with a 3020# race weight. With a better launch & more tuning I probably could have done better by a few tenths(famous last words) The Buick compressor is a T3 but is much larger than the stock turbo and uses a T04 S Trim wheel. Will this new huffer make a huge difference? Do I have 12 second potential from this overweight (the car not me )tank? After the turbo is in I'll probably go 3" with a straight through muffler on the exhaust. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 12, 2002 Share Posted July 12, 2002 With like drag radials and practice launching its my opinion that car could run into the 12's or close. With drag radials you also get to test out the U-joints and see how well they'll hold up. I might be wrong, but it sounds extremely traction limited I'd imagine at 15 lbs boost even at 3000 pounds (which is still lighter than a mustang by several hundred pounds and they run those into the 10's all the time, its just cubic money to do so... ). Regards, Lone Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 12, 2002 Share Posted July 12, 2002 Tom, I'm curious... how did your Z get so heavy? Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted July 12, 2002 Share Posted July 12, 2002 get it on there and go find out! Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 12, 2002 Share Posted July 12, 2002 If you have the stock turbine wheel, that is going to be your limiting factor. Kind of unclear from your post. My ZX is heavier than your car, and I have drag TA's and a much larger hybrid, so I would say you could break in the 12's, but if the turbine wheel is stock, I would not bet on it. Of course this is my opinion. A 3 inch exhaust will help. Good luck, the 50 trim should be a much better wheel than the GN one. Quote Link to comment Share on other sites More sharing options...
Guest Tom Scala Posted July 12, 2002 Share Posted July 12, 2002 That weight is for a 78 with me,1/2 tank of gas,a/c and an all stock body/bumpers, jack,spare,etc. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 12, 2002 Share Posted July 12, 2002 Tom, I am a firm believer in getting the most of the turbo you have before jumping to a bigger one and you are not close to the full potential of your current setup. As a point of reference, I was close to 300rwhp @ 17psi with a stock L28ET engine, SDS, SVO 36# injs, 300ZX 55mm TB, NPR, my DP and 3" exhaust. Very similar setups but you have a better I/C and turbo and I had a better exhaust system, the 3 things that are going to make your HP. That said, you should come close to matching me. My formula says 235rwhp with your ET/MPH/weight and 291rwhp for mine. Even if we want to be conservative, I would say there is another 40rwhp to be gained simply from tuning. It is quite unbelievabe the HP difference in a turbo engine not properly tuned. I have seen 60hp difference in one night from my 1st run to my last because something was off or I kept tweaking the fuel management. If it is just a matter of tuning or there is a real problem why you are not making more HP, a bigger turbo will make more HP but only mask a problem. BTW, given the same HP, a better 60' would give you a quicker ET but you would have a slower trapspeed. No matter, the ET is what counts unless you are just looking to see how much HP you are generating. Quote Link to comment Share on other sites More sharing options...
stony Posted July 12, 2002 Share Posted July 12, 2002 ok there it is again...... quicker 60ft times = slower trap speed???? i had a long conversation on this with a buddy before. I was thinking to get a faster 60 foot times youd have to be going faster at that point in the track then the slower time (higher MPH). now if this is right youd be going faster thru the traps too right? SCOTTIE!!! please set me straight on this and why. And by the way... is the trap speed actual speed like a radar guy or is it a calculation or something like that???/ thanks. Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted July 12, 2002 Share Posted July 12, 2002 OK ill jump in here. In my racing expoits I have indeed seen a slight improvement (sometimes) on MPH when i cut a better 60ft time. Makes sense to me because the 60ft time being faster means you have accelerated faster and have the opportunity to reach a higher speed because u are achieving speed (accelerating) faster by cuttin a better 60ft. However, MPH is a product of HP. You might gain or loose a couple MPH due to the cars line down the track, 60ft time, traction, chassis reaction etc..but even if you loose a full few tenths on the 60ft time, you should still run right about the same speed as if you ran a quicker 60ft. The 1/4 mile is enough distance for the HP to achieve roughly the same velocity no matter the traction at the line (within reason). my .02 Jason Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted July 12, 2002 Share Posted July 12, 2002 Oh, and... Trap speed is the actual speed measured over a set distance. The car breaks sensor beams at the finish line and at a set distance after the finish line. The computer uses time and distance to calculate the speed. For this reason you want to accelerate through the traps and beyond for an accurate MPH Regards, Jason Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 12, 2002 Share Posted July 12, 2002 Another one of those age-old arguments . What I described is going to be more prevalent in turbo cars simply because, given more time on the track, (as a result of a slow launch) to build boost under load, a turbo car will generate more mph. Jason is dead-on when he says MPH is a product of HP. However, if you use a formula to generate HP from ET, MPH and weigh, and weight and HP is unchanged, you cannot improve ET and MPH. The MPH loss I am referring to is not huge, simply because ET affects HP less than MPH. Let me relate an experience that happened just recently. I make a pass with slicks, cut a quick 60' and the car goes 10.86 @ 124.39. HP formula say 430.6rwhp. Next pass I make a minor tweak to fueling and get a not as good 60' and the car goes 10.95 @ 125.59. Formula says 435.3rwhp, about what I expected from the tweak. More HP, slower ET but more MPH. The next time to the track, I switch to the 17x8.5s and 275 DRs, much heavier! I got an horrendous 60' and the car goes 11.17 @ 125.59 (not a typo, the same MPH as the previous run). Formula says 427.5rwhp. Hmmm! SO I lose almost 8hp but the car goes 1.2mph faster? Yes, lousy 60' gave me more time on the track to build boost and mph. Given an extra .31secs on the top-end with that kind of HP and you will definitely have a higher top-speed. Lets play around with the formula and show how ET and MPH is affected by HP and vice-versa. We have a 2800lb turboZ that went 12.0 @ 115, generating 339.1rwhp. If the HP and weight was unchanged but the ET was quicker at 11.85, the formula says the mph would be 114.3. If the 60' was lousy and the ET went up to 12.15, the mph from the formula would be 115.7. Exact science, absolutely not, but it proves my point and my experience everytime. Here is another strange one I experienced. I ran against a 600hp SupraTT. He bobbled badly at the line and had a 2.6 60' and an ET of 12.76 but almost 129mph!! He just had a bad start that gave him more time to build boost and an extra second on the top-end with that HP is going to make a huge difference in MPH. For those with a passing interest, I probably rambled and the non-turbo guys are probably not convinced Quote Link to comment Share on other sites More sharing options...
stony Posted July 13, 2002 Share Posted July 13, 2002 ok kinda makes sense... but if the supra hooked of the line with you... wouldnt it make sense that his MPH would be higher, because he was going faster at an ealier part of the track therefore has more track to excellerate??? and next question... if mph is a calc over a distance will it be close to what your speedo reads across the line??? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 13, 2002 Share Posted July 13, 2002 Scottie I understand the whole thing, except I'm a bit confused where you said you got bigger DR's but cut a considerably slower 60' and ET. Was this due to a bad launch or was it actually the wheel/tire swap? You say the wheels are heavier, which would contribute to inert rolling resistance, but are also wider, giving a larger traction pad, compounds being equal between the two sizes I would imagine the tradeoff between increased weight/traction would be beneficial. The reason I am somewhat concerned about this is because I have a rather heavy set of 15x10's I was going to get a pair of 295 DR's for.. I couldn't find any 8.5-9.5" wide wheels and I got these real cheap, they actually shined up decent. But..... they weigh about 26 lbs apiece *gulp* I guess my question narrows down to.. how much does the weight of the wheels (or entire rotating assembly for that matter) actually contribute to 60'? I understand the "duh"- heavier things take more energy to move, but if you were losing traction before it seems like heavier would actually help you gradually lay down the torque. There's probably something obvious I'm missing here Wasn't this post originally about hybrid turbo's? -980mak Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 13, 2002 Share Posted July 13, 2002 Stony, Jason had the perfect description and as a result the MPH would be slightly higher than the speedo if taken exactly at the finish line. I go back to what I said before and the formula bears me out, Given the same HP and Weight, you cannot improve ET and MPH at the same time. A quicker ET means the car is spending a little less time on the track. The impact of the little less time is on the top-end where you have just that less time to build MPH. If the Supra did not bog and cut say a 1.80 (he had slicks or ET Streets), and you apply the 1.5x factor, his ET would have been around a more normal (for that heavy car) 11.60 and the formula spits out 123mph. That is a ton of MPH for an 11.60 but normal for a SupraTT. Mortal, err, normal cars running 11.60 would have about 117-118mph. 980mak, the "heavier" reference was in comparison to the Z-28 16x8s/slicks combo. The 16x8 are much lighter than the 17x8.5s and slicks are very light. That is the penalty you pay for going to a larger diameter wheel with wider tires. Just ask Terry Oxendale or Dan Juday what their wheel/tire combo weighs. As for why the 60' was so much slower (about .2 compared to my normal DR times), there are a couple of reasons. On the previous run that night, the car was backfiring during the burnout and fell on its face at the launch because the batt voltage was down to 9.5! A mad scramble followed to fix it and when I did, I just was not focused at the line. Those of you who run quick cars that launch hard know how important that is. The primary reason though is the fact that was the 1st pass on this new heavier, stiffer sidewalled combo and I just need time to find the right burnout/pressure/launch boost procedure. It is not a knock on going to big wide DRs. In retrospect I wish I could have stuck with the 16s but as pointed out several times, tire sizes are limited in 16s with 245 Nittos being the biggest, "normal" 15" wheels do not fit over the Vette rear brakes and certainly not the fronts. I do not have an answer to the exact effects of heavier wheels and tires, but going in I was willing to sacrifice a little 60' and ET to not have to stripe my shorts with the car wandering at 125mph. I just cannot get myself to put front skinnies on the car. One of these days I know I will have to, because I am probably giving away at least .2 or more in the ET becaue of the difference in weight and how much harder I could launch. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 13, 2002 Share Posted July 13, 2002 I totally gotcha now. I must agree on the "stripe" issue.. I've seen too many cars looking like this: / when the track is like this: | I remember that crazy run you had, and trying to keep the car away from DOOM. I don't mind getting a little sideways at 70mph, I just like to do it in the privacy of three lanes I think the 295's will work great for me ones I get the hang, just gotta whip up some flairs to fit the monsters under there. Hmm... -980mak Quote Link to comment Share on other sites More sharing options...
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