Why is it so damn slow

[JDSfastGN]

I've been working on my dads old 85 GN for a while now trying to get it figured out and I'm at a loss. The car has ATR headers, 2.5" DP, retrofitted TA49, cold air intake, LT1 MAF/translator, 87 ECM and module, ported heads with bigger valves, .030 over TRWs, home ported intake, ported throttle body, 50# injectors as well as a walbro 340, hotwired. The tranny is decent and has a TCS "supposed" 2800 12". The big ? is the camshaft amd converter. He had the cam installed years ago when the motor was rebuilt and does not know the specs or manufacturer anymore. The tranny was done at the time as well and since then its never been the same, although i did switch out the D7 that was in there for the TCS 12" thats in there now about 3 years ago. The car has no balls at all. From what ive read and seen tuned right it should be a low 13 sec car on pump gas and mid to low 12s on race gas. I've come to the conclusion that the cam is just completely wrong or the stall converter is a POS. The 49 spools pretty slow barely hitting 15 psi in 1st gear. The cars RPMs seem to rise very very slowly compared to other hotairs ive been in and compared to both intercooled cars in the family. On the footbrake it stalls to around 1900-2100 rpms before the peg leg breaks loose even with the parking break applied. I know stall can be dependent on power output so im not sure which is the big hang-up on the car. Has anybody installed a cam that was just completly dogged down a motor? It has a known good module, coil, no vacuum leaks, BLMs at 125ish, 02s at WOT are low 800s, TPS is .42 and 4.45 15 psi with no knock etc... I plan on doing a compression test tommorow to see if anything is noticable there. Any other ideas? I just recently did the intake, turbo, and injectors and it was slow even before those mods. Thanks guys, i know this is long winded and a lot of fluff but im just looking for some ideas. I think ive narrowed it down to a horribe cam choice, or degreed incorrectly (the car idles and drives great BTW) or a TC thats just soaking up all the power.

 

[BRAD_PADGETT]

Did you have a new ECM chip burned for your specific modifications? If not your car will run like crap. Just a thought. Brad

 

[racemybuick]

for a TA 49 and 50 # injectors, and especially ported heeads and intake, you should run a 3000 stall converter, and you definately want to know what cam, if not replace that cam with a 206, or the summit 204-214 job....without knowing what cam and not running a little higher stall...foot breaking 12 sec is not half bad!!!! If you can pull a 12 sec out of that car with those mods...you can easily drop to the 11's with a few tweaks!

Good luck....keep us posted...last step to greatness would most likely be alky injection, and crank up that boost!

John

 

[turbo6x2]

Does the car still have the cats on it? and if so are the plugged? If the car can't breathe is will run and boost like you have listed. Just a thought.

 

[JDSfastGN]

for a TA 49 and 50 # injectors, and especially ported heeads and intake, you should run a 3000 stall converter, and you definately want to know what cam, if not replace that cam with a 206, or the summit 204-214 job....without knowing what cam and not running a little higher stall...foot breaking 12 sec is not half bad!!!! If you can pull a 12 sec out of that car with those mods...you can easily drop to the 11's with a few tweaks!

Good luck....keep us posted...last step to greatness would most likely be alky injection, and crank up that boost!

John

haha that may have come off wrong, the car "should" run low 13s high 12s potentially with these mods but its not even with in a couple of seconds of a 12 at this point. If it was even in the 13s i would be happy for now.

Brad I have a TT chip on the way specifically for this setup and am running an older Jim Testa 50# chip that was burnt for my 87 GN when it had a similar setup. I know it may be a tad off and holding it back a little but it really can't be that bad I wouldn't think, the scan tool numbers are there.

turbo6x2, naw no cat on the car, other than only being the 2.5" DP that came with the ATR headers its about as free flowing an exhaust as you can get. The mufflers are straight through ATR pitbulls. I guess i'll wait and see how it reacts to the new chip before i really tear into it. The car hasn't been right for a long long time so
Thanks for the help guys, any other ideas are more than welcome.

 

[V6cious]

hey check to see if you have a garret housing that seems to be whats causing all the problems

 

[JDSfastGN]

Its a PTE .63 housing, but to be honest the car was a dog(a lot slower than it should have been) before the turbo/injectors/ported intake.

 

[alec296]

how old is the wastegate? it could be a problem if it is bleeding down.
also check if your getting knock retard. that is what mine seems to be doing
its pulling 9 degrees out of timing.check vacuum line to map(on right fender)
and see if it melted near the turbo.(common spot)
andy

 

[JDSfastGN]

how old is the wastegate? it could be a problem if it is bleeding down.
also check if your getting knock retard. that is what mine seems to be doing
its pulling 9 degrees out of timing.check vacuum line to map(on right fender)
and see if it melted near the turbo.(common spot)
andy

Its fairly new, but i have another i may try. I also may try running it tuner style, as the way it is right now its not very tight against the puck (barely have to pull it to get it onto the puck arm) Usually running tuner style on my 87 makes me have to tighten up the wastegate to achieve the same boost level thus keeping the puck sealed better helping spoolup. It doesn't knock at all, 15 psi and low 800 o2s. All the vacuum lines are brand since i replaced them while the intake was off. (vacuum lines on the hotairs is a PITA haha) Thanks for the ideas and keep em comin. I'm gonna play with it tommorow hopefully so ill see if anything changes.

 

[buickpower]

Is it too fat down low? what do you run for fuel pressure? other than a mechanical problem i'd also lean toward the chip or convertor. Also how long ago was the motor/tranny redone, and how is the car's top end power?

 

[JDSfastGN]

Is it too fat down low? what do you run for fuel pressure? other than a mechanical problem i'd also lean toward the chip or convertor. Also how long ago was the motor/tranny redone, and how is the car's top end power?

Hard to tell, the 02s look good and it doesn't blow any black smoke. 40 psi line off right now. The chip was sent to me yesterday so im hoping to have it this week. The motor has about 45,000 on it and was rebuilt in the mid 90s along with the tranny. The tranny was never right so my dad and i pulled it and rebuilt most of it ourselves early in 2001. It shifts well and at the proper time. The topend isn't bad(feels like a car that if it had bottom end may trap 97-98), once it gets rolling it will kinda freight train and build up steam. Even from a roll it seems to build boost slowly taking away any "snappy" feeling but once its rolling it pulls pretty decent but still not what it should imo.

 

[JDSfastGN]

Well i did a little testing on the car today. I did a compression test and all came back well within 10% on each cylinder but seemed a tad low compared to the results ive gotten on my 87 before. They were all right around 120-125 with the engine cold. But i hooked the turbo vacuum line up straight from the compressor housing to the wastegate and took it for a ride. I had to tighten the rod about 4 full turns to reach 15 psi again thus keeping a lot more tension on the puck. I have an RJC boost controller inline as well and now the car spools up fairly well and seems to pull through the lower gears quite a bit better. I'm probably gonna go hook up my old electric fan from my 87 on the car as the clutch doesn't seem to be doing its job after a few hard runs. But i would say the car seems to be what i would call a solid 14.00 car for now. I guess its a step in the right direction. I'm looking forward to installing the the turbotweak chip when it arrives later in the week. I still think the stall converter may be a problem but ill reserve judgment till later.

 

[forcefed3.8's]

Make sure the wastegate hole is not bigger than the puck. The precision housing might be set up for a large puck or external wastegate.

 

[buickpower]

hmm, maybe a post o2 but pre turbo exhaust leak, at either end of the up pipe connections? o2's can look normal but you can still be spitting out exhaust before the turbo. just a thought

 

[JDSfastGN]

Make sure the wastegate hole is not bigger than the puck. The precision housing might be set up for a large puck or external wastegate.

The wastegate hole is ported but the puck is a larger puck that covers it perfectly. buickpower, the only exhaust leak is at the DP to puck which isn't gonna affect anything other than leaking nasty soot on my freshly painted valve covers :frown: The up-pipe is sealed pretty well but ill get some hose and see if i can find anything else.

 

[JDSfastGN]

in that last post i meant downpipe to exhaust housing.... I just took the car out again and maybe it was only me being hopeful earlier but damn its still sloooowwwww. Not a 14.0 car. Oh well ill keep working with it

 

[bison]

The converter should stall more than yours does. The precision .63 takes more converter than a Garrett to spool as fast. The cam is a big what if but i doubt its effecting the car that much. You need to crank the boost on that thing and see how the performance is. Put in some good fuel and crank it. Better yet put on a meth injection system. It should mph around 105 at 22-25psi. What head gaskets were used? What block casting is it? The pre 109 blocks are taller deck than the 109. If you use a graphite head gasket on the early ones you lose about .4 to 1 compression unless the deck has been milled down. That would take away some power and make it a little more lazy on the bottom but you should be able to run a little more boost to offset it. You wont see the benefits of the turbo and heads till you turn it up, so crank it.

 

[JDSfastGN]

The converter should stall more than yours does. The precision .63 takes more converter than a Garrett to spool as fast. The cam is a big what if but i doubt its effecting the car that much. You need to crank the boost on that thing and see how the performance is. Put in some good fuel and crank it. Better yet put on a meth injection system. It should mph around 105 at 22-25psi. What head gaskets were used? What block casting is it? The pre 109 blocks are taller deck than the 109. If you use a graphite head gasket on the early ones you lose about .4 to 1 compression unless the deck has been milled down. That would take away some power and make it a little more lazy on the bottom but you should be able to run a little more boost to offset it. You wont see the benefits of the turbo and heads till you turn it up, so crank it.

Yeah the converter should stall higher(i have another 12" 2800 D5 brand new in the box from PTS but i don't know if i want to chance putting in a converter and it not performing well either, as i haven't had great luck with any restalled D5s) I may throw in a gallon of Xylene and see how it feels on 18 psi or so but i dont' have access to any good gas right now I would hope it should trap higher than 105 at 22-25 psi with heads/cam/ intake/ Ta49 etc... but maybe im expecting a little too much from it. ( I was thinking 108-110 on higher boost and good gas) Its a stock 85 block and i couldnt' tell ya what head gaskets were used, i would assume stock but I'll have to ask my dad to see if he remembers. Thanks again guys.

 

[bison]

Even with the ported intake the heads are being choked. Go for the meth injection and run the 25psi. 105mph was a low number. It could certainly go faster.

 

[WFO]

I bet it's rich.

Start lowering the FP about a PSI at a time and tune using the knock gauge.I bet you'll be amazed at how low the FP will be before you get any KR .