Ok my TTA is back running perfectly, finally got around to trouble shooting the code 42 this weekend and figured out it was a bad ECM. So I replaced it and Everything is Perfect.
So to see about the boost discussion we were having before about the Manual and Atuomatic cars, about loosing too much boost and what not with the 5-spped. Well here is the answer. From turbo link recordings of a run from a 5mph roll to about 4000rpms into second gear. Boost went from 0 to 16.1 PSI with 0 degrees of spark retard at 4000RPM in first, held till shift at 4700rpm. Droped to 9.5 psi at I think was something around 3000RPM into 2nd and built back up to 16psi by 4000rpms in second where I lifted and hit the brakes.
So as you can see ther is a significant drop in boost even in an auto car.
Though I feel this is attributed to two things. Needing a quicker shift to not loose as much boost. I am considering a shift kit now, and the fact that the turbo has to work so hard to pull air throught the factory Air Box. THis will be remedied by a Stainless steel MAF pipe, MAf Modification, and a 9"K&N. This should allow for quicker spool up, more boost soner and sustain boost while Shifting to have more power going into the next Gear.

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89 Trans Am Turbo 3.8L All stock 43,000 miles #1053 of 1555

Past Thirdgen:
86 Trans Am w/ built 355TPI with SLP goodies and too much other stuff to List. One sweet *** car, wish I would have had a good enough Job to pay insurance on three cars so I could keep it, but for a 89 Turbo Trans Am w/ Low miles, I think I made the right choice!

 

oh yea website
www.geocities.com/feltsb/kyle.html

 

Good information there Kyle...thanks

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-Bill

-=1987 Buick Grand National=-
Almost Jacked Up Like a Mother

*CC 218/218 cam, ported and polished heads (1.77, 1.50), Accufab AFPR, custom 3" DP by Custom Tubes, dual 2.5" exhaust, Bilsteins, Walbro 307 hotwired, Big Mouth cold air intake, 009s (42.5# injectors), custom PROM and 20psi of fury*
SOON to have alcohol injection

Wanna try me?

-=ICON Motorsports=-

Modertor TPI board

 

I try, but I was actually just answering the question from another post, What about you boost how much do you lose on your shift? I mean when you jack up to 20 psi or what not, does it fall off quick or Hold better?

 

Yes, I agree. But, since he has a 3.8 buick, most of the mods he applies to the engine doen't necessarily mean you can also apply to the 60deg, if youm want to turbo/SC it. Like for example the MAF. I'm sure you can finds many choices of MAFs for the Buick offered through the aftermarket, but try finding an aftermarket MAF for the 60 that was used in 87,88,89. He also has many intake choices to chose from. For the 60deg, you know how many aftermarket EFI (with EGR) intakes are available for the 60deg? ZIPPO.
To add to the depletion of boost when shifting, I don't know if TTA's come with a 5-speed but if they did they they would have had to add a BOV to prevent boost back pressure from slamming the compressor blades when the TBI butterfly closed between shifts. The GM engineers didn't think auto shifting was that important, to substantiate the boost loss, i guess.

 

Kyle, to tell you the truth, I don't think I've ever noticed a boost loss on a shift, never mind a 7psi loss. I am now running 16-17 psi due to my ailing turbo (new one arrived today ) and once it pegs, it's there and doesn't deviate. You are also running TL so it may be more accurate than my liquid filled boost gauge, but I would have noticed a drop like that. Was this at WOT? and it is shifting at 4700? Might want to up that a little to 5000, although, I would get it dynoed first and see where you should be shifting at. Sounds like a strong running car. Congrats
Best of luck

------------------
-Bill

-=1987 Buick Grand National=-
Almost Jacked Up Like a Mother

*CC 218/218 cam, ported and polished heads (1.77, 1.50), Accufab AFPR, custom 3" DP by Custom Tubes, dual 2.5" exhaust, Bilsteins, Walbro 307 hotwired, Big Mouth cold air intake, 009s (42.5# injectors), custom PROM and 20psi of fury*
SOON to have alcohol injection

Wanna try me?

-=ICON Motorsports=-

Modertor TPI board

 

the turbo 3.8L never came with a manual transmission. GM tested it out and saw that the stick cars were too much slower. If you want to run a stick you would probably need 2 smaller turbos insted of one big one like the TTA and GN have. That way there is less lag and less boost loss.

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-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

To be installed eventually far far far into the future: Yours if the price is right and I don't have to ship :
Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248), Catco 3" cat, and injector spacer.

Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options
AOL IM: superGRtaz

 

well.. sorry to say but go to a few import sites and find some boost controlers that do not allow boost to bleed off between shifts. It connects to the wastegate and does not allow the pressure to drop, or if it does it take sa LONG time to do so. much longer than it takes to quick shift gears. And with that little gadget you will out run an auto. Simply because you can hold the RPM's you want.

 

Tas you are right, the TTA with manual was slower (6-speed actually) by 1 second in the 1/4, but what is little known is that bastard topped out at like 186mph STOCK.

------------------
-Bill

-=1987 Buick Grand National=-
Almost Jacked Up Like a Mother

*CC 218/218 cam, ported and polished heads (1.77, 1.50), Accufab AFPR, custom 3" DP by Custom Tubes, dual 2.5" exhaust, Bilsteins, Walbro 307 hotwired, Big Mouth cold air intake, 009s (42.5# injectors), custom PROM and 20psi of fury*
SOON to have alcohol injection

Wanna try me?

-=ICON Motorsports=-

Modertor TPI board

 

The stick just didn't have the right gearing to utilize the turbo right. YEs GM would have needed to install a blow off valve, but they are easily availabe even in the aftermarket for the TTA and GNs.
I think my boost drop is significant and my shift point shows about 4700 or so. I was at WOT, but you should see some boost loss, Unless your down shift hits an RPM where you have fool boost through that gear anyway. This is because you lose exhaust velocity between when you go into the next gear due to the drop in rpm, but like I said if you are still in an RPM that will achieve max boost you will still have it.
I think that the mods I listed above with a better Down pipe will minimize that drop off, but as I remember correctly thats what my Brothers old 300ZX turbo would do to. Not as large of sum, but it would drop a few psi, but I think it was only a 10 or 12 psi turbo.

 

Hmmm......you would think that would be the opposite case for boost loss (not lag) if the turbo is a factor for this problem. Wouldn't a larger turbo, with larger turbine/compressor assembly allow for better inertia and be less prone to spinning down as quick as a smaller turbo that benefits from less lag? I'm certainly not a physics engineer but doesn't the diameter size of the rotation assembly contribute to it's ability to spool or unspool in the same manner, i.e,. the smaller the diameter the quicker/easier the responce to be pushed?

QUOTE]Originally posted by Kyle F:
The stick just didn't have the right gearing to utilize the turbo right. [/QUOTE]
Yes, that could be the case. Could also be that the person doing the shifting has to be quick enough to power shift before allowing the tubos to spin down to excessively. Maybe that person who test drove it is not a Bill Jenkins? The increase in technology for improving the performance of the Auto for drag racing makes the manual less desirable these days. Fewer drivers prefer autos, thus having less exposure to the need for power shifting. For road racing, manual is still the way to go.

 

Nope 2 smaller turbos will spool faster and have less lag than on larger on, but takes a whole lot more sapce and $$$$ to build one.

 

Yes I gree. Thats not what I was trying to point out. Please re-read my post.

It's a fact that a small turbo will spool faster. But, for spooling DOWN quicker, one would think that would also be the case that a small turbo would do well. Thus, if the problem existed when using a small turbo, that boost will be lost between shifts, a larger diameter/circumference wheel should remedy this by maintaning boost due to it's better inertial (sp?) qualities.

 

You got it backwards. The heavier wheel will want to spin longer and maintain speed yes, but it will put more friction on the bearings or oil pad that it travels on where the lighter one wouldn't

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89 Trans Am Turbo 3.8L All stock 43,000 miles #1053 of 1555

Past Thirdgen:
86 Trans Am w/ built 355TPI with SLP goodies and too much other stuff to List. One sweet *** car, wish I would have had a good enough Job to pay insurance on three cars so I could keep it, but for a 89 Turbo Trans Am w/ Low miles, I think I made the right choice!

 

This is debatable. Checkin some reference material on turbos and their characteristics I found no information alluding to this theory. I did find that the smaller the turbine ( assuming of course that the housing is of the same proportion based on the AR rating) the greater the amount of backpressure towards the exhaust ports. If breakpressure exists, there is an impedance created from this that minimizes the efficiency of the turbine from spinning.
I don't know if this is your problem though it's a given that automakers tend to undersize their systems a bit to lower the powerband (except Porche!) to between 2500/4000 RPM which would appeal to typical evryday driving habits. Thge AR rating of your turbo must be known to bear this out. I would think your problem would be solved by getting a larger turbo. But that's JMO.