Updated track passes and Converter efficiency concerns

JDSfastGN

Well-Known Member
So a while back I posted this thread about finding my bottleneck. The car had been 10.61@127 in that post and I just wanted to update. The car can and does 60 in the mid to high 1.4s but driver issues and rushing at the line preventing me from getting there on this trip. So im still looking mostly at 1/8th mph and 1/4 mph
https://turbobuick.com/threads/trac...find-my-bottleneck.457655/page-4#post-3812441

I swapped to an SD chip setup, 4" intake with a 1" plenum spacer and, adjusted the governor and got a 5700-5950 shift point. I turned the boost up a bit and had it tuned for 30-32 psi at sea level but the altitude and density altitude seemed to have dropped that considerably once I made a pass up in Oklahoma. A few small issues prevented me from making more than 2 qualifying passes at the Buick vs Ford Shootout. The car ran well enough. On my first qualifying pass it went 10.69@128.66 with 27ish psi down low and 28-29 up top having to let out for the 1-2 shift for some reason when it went to 6200 and kinda laid over. The 2nd pass the boost controller seemed to hit its limit and dropped boost to 22 so it was a throw away.
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In the finals I didn't get the chance to build much boost as I was trying to tree my opponent who sat there for what seemed like an eternity after I went and still ran me down by 30 mph. The car trapped 129.5 running 28-29 psi up top. timing was 19* throughout the run. Really close to 130. All powerlogger mph is off due to being on 28x9 vs my 315/35/17s that its calibrated for.
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Soon after Oklahoma I hooked up a 2nd MAP sensor to the intercooler pipe right before the intercooler to see the pressure drop. At 28-29 psi it was only 2-2.5 psi drop. At 32-33 psi it was closer to 4 psi drop. You can see one screen shot attached.
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So what my question here is, in February my engine spun a cam bearing. The block came back with no cracks so the cam tunnel is being line bored to fit the same bearing size as the outter bearings. My biggest concern is still the converter. Its a PTC 9.5 16 blade with a sprag. According to the TCI calculators slippage was around 12-13% on my passes. Should I consider getting it adjusted again? Ive been working on my dads silver T recently and his 17 or 18 blade PTC and it was 4.5% at 130 mph on 26" street tires and running 6000 rpms. His has a 3.42 rear gear vs my 3.23. His car makes similar power to mine and our 80-120 times were very close. Should I really start considering going to a 3.42 again? Can that small amount of gear difference have that big of an effect?

I don't have any backpressure data but plan on having a bung welded into my new to me TA headers I picked up. Not sure if there's enough data to determine much but while the car is down and the engine is out I figured Id get some ideas.
 

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750H.P.V6

Brutal 6 Racing
You have a lot of good data included in your post. I looked thru most of it and honestly the convertor doesn't seem to be excessive loose. 2 things that lead me to believe it might be a bit looser than you need / want is that you say the car will 60ft in the 1.4X range which i would say is not typical for a high 10 second car . Secondly the MPH gain from the 1/8th to 1/4 miles seems slightly low unless your racing into a headwind. On another note I notice you're not running much timing and your A/F ratio seems very conservative. Please don't take any of this the wrong way, just observations. The car looks great BTW.

Neal
 

Mr.Spool

Well-Known Member
Can that small amount of gear difference have that big of an effect?
Gear are torque and are a mechanical advantage.back in the day,my 10 sec stocker with a 49 turbo had a weight of over 3800lbs.my fastest times were with a 4.10 gear.on the high horsepower combos that are lighter, 3.23 and lower trans gearing can work but not on the heavy cars with mild builds.
 

TurboTnZ06

Go on red!
One way to test the theory, drop the boost to 17-18 or then 20-21 and see if its the same mph. I was blowing through my converter a PTS 9-11 LU that wouldn't lockup and more boost just meant slippage, like 16%+. Ran 10.50 at 125 on 17-18 psi boost or 25+ psi boost, but it'd just sit at 6200 the whole way and not go any faster than 130. I run a PTC 9.5 17 NLU now, but haven't been to the track since 2015, but it sure does feel like that fixed it on the street for sure.
 

JDSfastGN

Well-Known Member
You have a lot of good data included in your post. I looked thru most of it and honestly the convertor doesn't seem to be excessive loose. 2 things that lead me to believe it might be a bit looser than you need / want is that you say the car will 60ft in the 1.4X range which i would say is not typical for a high 10 second car . Secondly the MPH gain from the 1/8th to 1/4 miles seems slightly low unless your racing into a headwind. On another note I notice you're not running much timing and your A/F ratio seems very conservative. Please don't take any of this the wrong way, just observations. The car looks great BTW.

Neal

It would have been a 10.4X pass on the last one had I been able to build boost at the line. Mid to high 1.4s seem pretty common for a mid to low 10 second capable setup imo. It picked up 26-27 mph as well which is pretty solid for a mid 10 car through my experience. I had the timing at 19* max since i had it tuned for 31-32 psi here in Houston but couldn't get it above 29 in Oklahoma. Target a/f was 10.8 on both passes. It tickles the knock a bit at 11.0-11.2. I definely don't take it the wrong way. I posted to get all the responses I could haha. Thanks for the compliment on the car.
Gear are torque and are a mechanical advantage.back in the day,my 10 sec stocker with a 49 turbo had a weight of over 3800lbs.my fastest times were with a 4.10 gear.on the high horsepower combos that are lighter, 3.23 and lower trans gearing can work but not on the heavy cars with mild builds.


I missed that i had any responses. I talked to Dusty last Friday. I'm going to go ahead and order a set of 3.42s and see how that helps or changes things and if nothing else it eliminates it as a culprit if nothing changes.
 

JDSfastGN

Well-Known Member
One way to test the theory, drop the boost to 17-18 or then 20-21 and see if its the same mph. I was blowing through my converter a PTS 9-11 LU that wouldn't lockup and more boost just meant slippage, like 16%+. Ran 10.50 at 125 on 17-18 psi boost or 25+ psi boost, but it'd just sit at 6200 the whole way and not go any faster than 130. I run a PTC 9.5 17 NLU now, but haven't been to the track since 2015, but it sure does feel like that fixed it on the street for sure.

I don't think I'm blowing through the converter or anything. It definitely slows down on lower boost. I turned the manual controller too far on my 2nd pass not shown here and it did something weird. Boost was only 22-23 and it only trapped 124 i think. This converter actually seems to become more efficient the harder I hit it.
 
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