North American Turbocoupe Organization



big turbo issues 88TC
ernie88TC Offline
Junior Member
#1
Have a (T3 or T4-- i didn't build it 8) on my new motor. Stutters if you get on it (worse if it's cold), but will take the boosted boost if it's about 3500 or up. i think the issues (occasional high idle related?) have to do with a mismatch between the injectors and the airflow, which makes me think it's a matter of the stock ECM vs what's needed.

i read thru the performance thread on turboford and found some ideas for a custom controller (LA3 ... Megasquirt etc), but i know you guys will know the "best" answer. i don't want to build a drag car, just a hotter but pretty much stock TC, so what is best?

thanks in advance, ernie Harkins
ernie
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Jeff K Offline
Administrator
#2
A T4 or T3/T4 hybird is way too big for an unmodded "pretty much stock" engine using the stock injectors, stock cam, and stock PCM. If you dont know the specs of the turbo, you obviously cant look at the compressor map to see if you are anywhere near the surge line.

Do you have a wideband O2? If not, you need one, even with the stock components, to be sure you are running reasonable A/F ratios under various RPM and boost conditions.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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ernie88TC Offline
Junior Member
#3
OK, i get the basic problem, which i think confirms my seat of the pants idea that the mix is wrong.

by "Wideband O2" i translate that to a "mass oxygen sensor? i had a guy suggest that i might want something like an 05 Mustang 6cyl mass ox, but next question got right to the "controlled by what" questions and he punted.

based on your answer, might just be best to drop back to a stock turbo, but i DO like it when it's "on".

thanks, Ernie
ernie
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Pete D Offline
Administrator
#4
The stock air/fuel (O2) sensor is a "narrow band" device. A wide band O2 sensor covers a larger range and is also the type needed to interface with aftermarket engine management systems. This sensor measures certain gases in the exhaust gas to display the amount of O2 (oxygen). This is different from a "mass air sensor" which measures
the amount of all air (not just oxygen) flowing into the engine though the intake tract (air filter to throttle body) Our stock engines use a VAM (vane air meter) which does some/much of the same thing the Mass air sensor does, just a different approach to measuring air flow into the engine. You cannot just swap out the VAM and install a Mass Air unit, it isn't that simple.
You could probably upgrade to a straight T3 turbo and be alright although some mods like a better exhaust system would maximize the gains from the T3.

How much boost were you trying to run with the T3/T4?
Pete Dunham


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ernie88TC Offline
Junior Member
#5
ok, understand wide band now.

sounds like i would have to go to a newer eng mgmt system to make it work, which is maybe where it would have to go anyway.

the boost is pretty high (15 or so), and when it starts stuttering, if i back off the throttle it goes ahead and increases rpm; ie, too much boost for the amount of gas.

have apparently got some rework on head and exhaust (3" pipe and free flow muffs no catalytic), so where best to get a plain t3?

is there someway to just dial back the turbo and mimic a straight t3?

thanks, ernie
ernie
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anasazi4st Offline
Senior Member
#6
ernie88TC Wrote:is there someway to just dial back the turbo and mimic a straight t3?
IIRC, the 1983-86 used a T3 turbo and the 1987-88 used an IHI.

As I understand it, the T3 takes longer to spool up but has a stronger boost; the IHI spools up much quicker but delivers slightly less boost. From what I’ve read, this is generally better for urban driving...if that also applies to you.

So, to keep your TC as stock as possible (which I believe months ago was your stated objective), and without upgrading/modding the engine, you would want an IHI, not a T3. That’s what was originally designed for your car. (Of course, since you already have a T3 then those mods were probably already done. The question is: would you consider reverting to an IHI?)

Recently I acquired a used IHI as a spare with plans to rebuild it. I did a lot of research on IHI vs. T3 and T3/T4 hybrid models, and the above paragraphs are a small regurgitation ;-) of what I got from that. I decided to stick with the IHI, hence my purchase.


Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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Jeff K Offline
Administrator
#7
Get the compressor map for the turbo. Possible compressor surge issue.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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ernie88TC Offline
Junior Member
#8
OK Jeff, thanks for that.

Sounds like i should go for an IHI and be happy 8)

So anybody got a IHI turbo?

Another issue: i am having some "wandering" in the steering, which made me think the caster is wrong. Alignment guy said it is a little off, but you can't adjust it. Then i heard about and adjustable plate gadget for Fox body Mustangs, but then i hear that "that won't work on a Tbird though.

i'm sure someone here has been through that already, so what do i want?

thanks, ernie
ernie
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