99VetteFRC

I took the car out to the track a few weeks ago and my 60 times really suck. I was just wondering if anyone in the section could help me out. I have full body and weight 70 Chevelle, 4.8/th350, 4000 stall, 4.10 gears, twin turbos (.63 exhaust/50 compressor). stock engine, with 80 lb/hr injectors. 30" tall slicks. I was also very hot and humid that day. I am car 5 on the time slip. attached are the tune and log of the pass. Seems the pulls really hard after 60'.

72chevy2

iTrader: (1)

What RPM are you leaving at?

Trans brake?

What two step rpm?

Twin turbo c5

That's not bad at all. It could come down to track conditions and what boost your leaving at. I've never had a turbo car do better than a 1.50 60 foot in my heavy street cars. I have a friend doing 1.43 's in his Camaro it just comes down to converter stall speed, tires and track conditions and a lot of times size of the turbo.

jridenour31

Leaving with boost?

jridenour31

Um, a 2.2 60' is awful.

Chicago TDP

iTrader: (3)

Any time I had a bad 60 foot it was one of the three:

1. no boost off line (lag)
2. Tire spin bad (no hook, bad tires, too much gear)
3. motor bogs due to too much hook and not enough torque.

I would say fist off, you only pick up 25 MPH from the 1/8th to 1/4
That tells me your 4.10's are killing your top end.
Also, with a better gear(3.55 possibly depending on tire size) your 60 foot should improve.
With a better great, it is going to load the turbo more and build boost better.
The 4.10s are just "too tall" for a big chevelle with twins.

My .02 cents... I could be totally wrong..just things I have done with cars in the past.

Twin turbo c5

oh sorry . yeah that sucks. how much boost you leaving at ?

Twin turbo c5

I personaly don't have luck with a low gear on a turbo car the more load you can put on the motor the quicker it will spool from my experience low gears hinder that load. . I've always had good luck with 273 to 355. I run 273's now . works great.

MIGHTYMOUSE

iTrader: (59)

i tried to come up with a solid response but cant put together anything legit. sorry dude.

emergency brake on? flooring it?

it should be 1.x on motor alone, even with stock 5.3

when you launch is it just going up to rev limit and you click 2nd 3rd immediately?

what does the trans fluid look/smell like?

do all 8 spark plugs look the same?

Wicked69

I run a full weight 69 Chevelle daily driver, sound system, etc. Twin Chinese turbos on a junk yard engine, 3.42 gears, and power glide.

When I had 3.90's and TH400 a 1.51 was my best 60ft. Switched to a powerglide and 3.42's and car built boost a whole lot easier. Car now does 1.40 pretty easily.

I also had good luck building boost a little on footbrake before hitting Tbrake. Even then part throttle on Tbrake did the best.

Hope this helps

98Camarod

iTrader: (43)

With a quick glance at the log, you are using a maf, no 2 or 3 bar map, leaving off the footbrake with no boost, no wideband to verify afr, fuel trims are jacked up.

What fuel are you running? your are running 21* through most of second then the timing drops to 16* in third. Seems odd.

99VetteFRC

I do have a wide band but the basic HPT can't log it. I can get it to build boost with 3.08s but I can't drive the car around cuz of all the hills around here. With 4.10s it wants to spin the tires before it builds boost off the line. I leave at 2k rpm but it is not building boost and doesn't spin the tires off the line. i thought maybe someone could help with a little tune adjustment to get 60' down some.

Tally TransAm

iTrader: (17)

rear drums? out of adjustment? may wanna double check and see if you can get more on the foot brake before the rears wanna spin

also the tune needs work, timing issue are likely why your mph is down, but trims indicate a fueling issue also. correct that and take a look at the pass bank because there is a substantial variance in fueling between the two

iat table is pulling 6-7 degs by the end of the run, something else is also though. didnt dig that deep into it

98Camarod

iTrader: (43)

why don't you have a 2 bar software? How much boost were you running?

You can log your afr through the egr, there are quite a few threads about it on hptuners.

99VetteFRC

I will check that out, thanks. I have a 2bar map and software but the car needs to be tuned with it. It only has a street tune, it won't run when I put the 2bar sensor in it and the software.

98Camarod

iTrader: (43)

But you currently have a 1 bar? All you have to do is install the map, apply the software, and do a write entire. When you log it in the scanner make sure you have the correct pid being logged. Get your wideband wired up through the egr and ditch the maf. Let me know when you do that and I have a nice map that should be a nice starting point.

99VetteFRC

If I put my 2bar map in and remove MAF, I need to scale for map and adjust for injectors.

98Camarod

iTrader: (43)

Was that log with the 2 bar map installed?

Exidous

iTrader: (11)

There are multiple things I see going on that are hindering you. Most have been mentioned.

You need a 2 or 3 bar MAP to run anything up to and over 14.7psi. You can run MAF only but you'll choke it pretty quick in front of a turbo.

An HPT Custom 2/3 bar OS should be used. $100 in credits if you don't have any spare.

Dump the MAF. Where is your MAF located? Pressure side or intake side?

Log WB via EGR or A/C pressure switch. A/C is most common I think.

Holy timing bat man. The spark tables need work. 36* is pretty dang high.

I suggest getting to the Custom OS and get the VE dialed in. Your injector values should be a fixed number. They should never change to get the fueling you want. That's what PE/BE/VE are for.

A 3.55 gear would be a good choice for stock motor maybe even 3.23. 3.73 if you have a less mild cam.

99VetteFRC

I already have HPT 2 bar downloaded. I also have a 2bar map sensor. When I install both the car runs until closed loop, then won't even idle. That is why I used the MAF. I am putting an LS6 cam in the car next week. When I get the cam in and figure out how to wire and log WB I'll switch to SD software. Does this really change low end power though? Seems to run pretty good top end.OH, yeah! My MAF is right before the TB.