Question about TTA vs. GN

[84gnguy]

What allows a factory TTA chip to run 16.5 lbs./boost and 26* timing and a factory GN to have 14 lbs/boost max. with 21* of timing?

What is the difference between the GN and TTA as far as the engine,turbo,fuel system,etc. ?

 

[Who Needs 8]

What allows a factory TTA chip to run 16.5 lbs./boost and 26* timing and a factory GN to have 14 lbs/boost max. with 21* of timing?

What is the difference between the GN and TTA as far as the engine,turbo,fuel system,etc. ?

Heads are different, better flowing exhaust valves. Just off the top of my limited TTA knowledge, compaired to some of the other guys here.

 

[Lee_Burough]

An Oft discussed point in history....

What makes the 20th Anniversary Turbo TA so special is that it is a complete mechanical package, and not just some tape stripes. Starting with the engine, Pontiac borrowed Buick's 3.8 liter (231cid) V6 turbo powerplant from the fabled 1986-87 Grand National. Some difference exist between the TTA motor and the GN version. Different heads were necessary in order to squeeze the motor between the strut towers. These heads, adapted from the transverse FWD version of the 3.8 liter motor, have the added benefit of improved exhaust flow and combustion chamber design. Subsequently, different pistons were required in order to maintain combustion chamber volume. Other changes to the TTA motor are a cross-drilled crank, larger 12 fin/inch GNX-style intercooler in place of the GN's 10 fin/inch design, specially-designed stainless-steel headers, higher-pressure Bosch 237 fuel pressure regulator, and a recalibrated engine control module.

The stock turbo is the same on the outside (some have mentioned a larger wastegate puck hole for the TTA, but I've never noticed the difference from stock Buick). The TTA Downpipe flows a little better. We know too that the Fuel Pump had a greater flow capability and was fed by a stranded copper wire (same pump as the Sy/Ty pump). I'm not sure about the factory timing in the chip....Didn't think it was significantly different than the stock GN chip (perhaps the wastegate solenoid was controlled differently than the GN for more boost...?). The TTA brakes and cooling system (special oil cooling system added) were upgraded significantly too....They weighed a couple hundred pounds less than the GN and they cut wind better (but, I wouldn't call the TTA a 'Fart Can' -pun intended ). All of the differences made the TTA about 0.7 faster in the quarter mile and 161 mph average -171 mph peak- speed around the Indy Track

:biggrin: :biggrin:

 

[89ICBM]

What allows a factory TTA chip to run 16.5 lbs./boost and 26* timing and a factory GN to have 14 lbs/boost max. with 21* of timing?

What is the difference between the GN and TTA as far as the engine,turbo,fuel system,etc. ?


When all is said and done, the basic difference is the dish of the pistons. The TTA piston dish is 6 cc's larger than the GN which allowed for a lower compression ratio and more boost with out detonation. The dish on the TTA is 30.4 cc's the GN is 24.4 cc's.

 

[UNGN]

The TTA head castings are much cleaner and Intake short side radius is much better than a typical buick head. The Chamber shape and surface roughness is much better and is less prone to detonation.

I've read that the orifice in the wastegate hose is smaller on the TTA. I know years ago, vendors were selling NOS wastegate hoses that were resulting in 17-18 psi of boost on a T/R. The correct T/R orifice is .050" diameter.

 

[1BADDAM]

The TTA head castings are much cleaner and Intake short side radius is much better than a typical buick head. The Chamber shape and surface roughness is much better and is less prone to detonation.

I've read that the orifice in the wastegate hose is smaller on the TTA. I know years ago, vendors were selling NOS wastegate hoses that were resulting in 17-18 psi of boost on a T/R. The correct T/R orifice is .050" diameter.

Exactly. :wink:

TTA's are .040"

 

[Matt Sando]

the TTA had a different fuel pressure regulator too witch allowd more boost.

 

[84gnguy]

Guys,thanks for all the info.
The reason whay I ask is,I was runinng a TTA chip in my 87 GN,and let me tell you..what a blast.But I would hear detonation at the top of second gear somtimes,and then Eric from Turbo Tweak mentioned the TTA chip has 26* of timing.I kept the chip in,and mixed 93 octane with some Sunoco 110 just to continue having some fun without hurting anything.My GN is basically stock other than some exhaust work and a rebuilt motor.Just got a chip from Eric that gives the same boost as the TTA,but less timing.Still fun
But that TTA chip pulls HARD in second with that 26*!!
So I know you TTA guys are having fun

 

[trading t/a]

the intercooler could have played a part in lowering the inlet temps of the air charge once compressed. With more fins per inch it would theoretically be able to disipate more heat, but does it matter at 16psi, that is the question.....

 

[Razor]

Actually the TTA chip had less timing than the Buick chip. I have .bins for both. Plus the TTA ran higher fuel pressure.

Compression ratio is the same.

Wanna know the secret.. its the rockers. 1.55 for the GN vs a 1.67 for the TTA. Using the same cam, the TTA now has more lift and duration. Combined with a slightly out the box better head, better IC, and better aerodynamics.. You can see the advantages..

Those engineers got thinking when they made the TTA.. too bad nobody knows bout them.

 

[TClassic]

Actually the TTA chip had less timing than the Buick chip. I have .bins for both.

Well according to Eric the TTA had full throttle timing of 26d after 4500, and 24d below 4500....I DOUBT the GN had more???????????

Can you somehow post the .bin, I only ask cause I have Eric making my TTA Chips!

Thanks

 

[1BADDAM]

Actually the TTA chip had less timing than the Buick chip. I have .bins for both.

Well according to Eric the TTA had full throttle timing of 26d after 4500, and 24d below 4500....I DOUBT the GN had more???????????

Can you somehow post the .bin, I only ask cause I have Eric making my TTA Chips!

Thanks

26* is close to a race chip. I thought stock timing was 19*

 

[84gnguy]

The factory 86/87 GN chip has 21*

 

[Razor]

Actually the TTA chip had less timing than the Buick chip. I have .bins for both.

Well according to Eric the TTA had full throttle timing of 26d after 4500, and 24d below 4500....I DOUBT the GN had more???????????

Can you somehow post the .bin, I only ask cause I have Eric making my TTA Chips!

Thanks

I believe on GN/T-type.org the .bin was posted somewhere. Eric doesnt need your .bin. He does need you to have the car in proper tune tho for his chip to work wonders .. And he's made a bazzillion chips...the stock image is one he'll never need for anything.

 

[2QUIK6]

I've got both chips, factory originals out of my cars, at 4800rpm and Load of 256, the TTA has 26.0 degrees and the GN has 22.1 degrees.
A stock TTA chip has way too much timing in it for todays sorry fuel, no way would I go WOT with 26 degrees of timing today on pump gas and no alky.

 

[Razor]

I stand corrected..it does have 26 degree's past 4400 RPM's at load values over 192.

 

[83ttypecooled]

stock proms

Hi,
My TTA has no trouble with today's gas, can't believe yesterday's gas was too much better.I tested the boost gauge in my car, very close ,within a pound or so of accurate. Of course, don't know about spark timing variations, but the only detonation I ever saw with my car's stock chip was when I pulled the wastegate actuator hose and plugged it. The car ran like a raped ape, but had slight detonation when the boost gauge pegged at 20.
On the other hand, my TType is a detonation hassle at all times. I can't seem to get that one right. I can not run pump gas at even low boost levels without trouble, have tried a lot of stuff. Time to pull the heads and see what has transpired, I think. Never tried a load of 100 plus gas though.
I agree that the TTA configuration is much easier to deal with, and that the Pontiac engineers did the job right.If Buick people had just had some more time to refine things, we probably would never have to deal with detonation and it's siblings!