??? So what is causing new issue with 70hpq

[boostingbuick]

Ok, I am helping one of the board members with his 87 GN. He removed a t45e turbo and installed a 70 hpq turbo. Nothing else was changed. Now when he stands on it the car surges or bucks and will on occasion, backfire. The old turbo was a 3 inch in and 2 inch out. The new turbo is a 4 inch in and 3 inch out. However, the inlet pipe is a 3 inch with a 3 to 4 hose and the outlet has a 3 to 2 1/2 for the 2 1/2 inter cooler piping. I find it hard to believe the pipes could cause this but nothing else has changed. If you slowly tip into it to wot it seems to be fine. But sometimes will buck. However, if you mat it, it will buck all the time. Boost was 20 psi on 110 race fuel.

----Now the things I did.-----


Replaced plugs - r42ts plugs gaped at .30

ohmed wires. Magna core wires - 4.0 ohms. Switch wires with my car and no change.

Swapped coil pack and module with my car.

Inspected fuel pressure under load to insure it was not falling off.

Inspected A/F with a wide band. 11.8 at WOT when it does run good.

Inspected TPS at idle (.44) and slowly went to WOT and had no issues.

Swapped out Mass air with known good one. (stock M/A)

Inspected all air hoses and inter cooler. V2 front mount.

No codes present.

All other sensors working good. Coolant-air temp-tps and etc.

Inspected to insure cam sensor was not 180 off. Was not.

Ran with dump open and closed, no difference.

Added ground from Ignition module to firewall. ( redundant )



Any idea's?

 

[boostingbuick]

I also replaced the 02 sensor, the old one failed.

 

[NCTURBOS]

I'd verify the wideband #'s and also run a powerlogger on it. Knowing the car... My first thought is a lack of fuel volume and psi, with the single pump.

Does it start to hestitate and backfire in a certain gear, or rpm, or boost range?


K.

 

[boostingbuick]

Not a fuel volume issue. I watched the fuel pressure during the issue. It happens at med. to higher rpm ( under 5k ). I have seen the a/f and o2 readings to be close under wot. I would expect fuel pressure to fail off befor it went lean. This is very hard to explain, but does not happen the same way every time. I mean holy crap, I spent 7 hours beating my head on this thing.

 

[johnnyttype]

compressor surge possibly?!?!

i have a link to a pretty cool website that has a lot of compressor maps and math equations to plot different engine combos onto the map to see how they compare and what not! try it out

Squirrel Performance - Turbo Calculator Version 4

 

[NCTURBOS]

compressor surge possibly?!?!

Usually compressor surge is more of an issue under part throttle and when you are having to peddle the car. Not so much w.o.t., I believe.

K.

 

[NCTURBOS]

It happens at med. to higher rpm ( under 5k )

So if you go w.o.t. from a dead stop or a slow roll... The car acts fine until the mid-top of the gear? Does it do it in all gears?


K.

 

[ghall]

So if you go w.o.t. from a dead stop or a slow roll... The car acts fine until the mid-top of the gear? Does it do it in all gears?


K.

Yes to both.

 

[johnnyttype]

Usually compressor surge is more of an issue under part throttle and when you are having to peddle the car. Not so much w.o.t., I believe.

K.

yea, i mean i was just lookin at the graphs for a 70 trim turbo and it was on the surge limit line for most of the graph. Plus i was thinkin that 20psi is not enough for that turbo so it could act like its at part throttle because it is not in its optimal operating zone?! make sense im just throwin ideas out there

 

[boostingbuick]

I don't believe it to be a surge issue because if we slowly go to wot and it does not due is buck, it will shift and keep accelerating till I let off. It pulls hard when it runs good.

 

[Chuck Leeper]

"I'd verify the wideband #'s and also run a powerlogger on it."

X2.

 

[NCTURBOS]

Yes to both.

I've got a few Armstrong double-pumpers NIB... :biggrin: Let me know when you want one... :tongue:


K.

 

[ghall]

I've got a few Armstrong double-pumpers NIB... :biggrin: Let me know when you want one... :tongue:


K.

Fuel is not the problem.
Car is on renegade 118(VERY SIMILAR TO C-16). O2's are very good and not dropping. Widebands are very good and not dropping.
Car runs VERY strong when easing into the throttle...only problems are when going full throttle in a hurry.


Geoff

 

[NCTURBOS]

Fuel is not the problem.
Car is on renegade 118(VERY SIMILAR TO C-16). O2's are very good and not dropping. Widebands are very good and not dropping.
Car runs VERY strong when easing into the throttle...only problems are when going full throttle in a hurry.


Geoff

Do you have a Direct Scan or Powerlogger file I can look at? If so, let me see one of easing into the throttle, and another of the full throttle in a hurry. Does it show any knock retard??


K.

 

[Scott231]

Why blame the turbo? Sounds to me like something else has "decided" to fail, coincidentally at the same time you changed turbos.

 

[ChavoLC2]

Put old turbo back on

If everything is checking out fuel wise, a/f, powerlogger, wb, etc etc.You could put the old turbo back on (pita) and see if it goes away. If the car runs great then I would suspect new turbo causing the issue..

 

[ghall]

If everything is checking out fuel wise, a/f, powerlogger, wb, etc etc.You could put the old turbo back on (pita) and see if it goes away. If the car runs great then I would suspect new turbo causing the issue..

Old turbo is not available. I sold it, I have had this turbo(70 HPQ) on the shelf for 6 months, and only put it on because someone wanted the old turbo. Trust me, if it was still here, I would have no problem with swapping it back on!
I ordered several new o2's today,
ordered all piping to swap over to 3" piping for the in/out of the intercooler. Should have this fabbed up and installed this weekend
I tried to order a powerlogger from full throttle---I haven't had any luck with getting in contact with them. I will try again tomorrow.
I will also be inquiring about their 4" inlet w/ maf.

I called Precision today. They didn't feel like the undersized int. piping is an issue at all--they had no suggestions.


Geoff

 

[NCTURBOS]

Old turbo is not available. I sold it, I have had this turbo(70 HPQ) on the shelf for 6 months, and only put it on because someone wanted the old turbo. Trust me, if it was still here, I would have no problem with swapping it back on!
I ordered several new o2's today,
ordered all piping to swap over to 3" piping for the in/out of the intercooler. Should have this fabbed up and installed this weekend
I tried to order a powerlogger from full throttle---I haven't had any luck with getting in contact with them. I will try again tomorrow.
I will also be inquiring about their 4" inlet w/ maf.

I called Precision today. They didn't feel like the undersized int. piping is an issue at all--they had no suggestions.


Geoff

You're running a Turbo Tweak chip correct? I think he stocks the Powerlogger as well.


K.

 

[8AV8]

.

 

[XXQUICK6XX]

I personally would try and match all piping to the same size. I just don't like the idea of a step up which could cause turbulence in the air stream coming into the compressor. Especially right at the housing. Plus the turbo is going to pry want a different tune. Also that 11.8 seems a little lean at wot.

Steve