Boosting Problems...

[Eric_Odie]

my friend owns a 1990 Supra Turbo, and at like 5K RPMS the boost gauge shows he's boosting out 8psi. I own a 89' and at 4K i'm boosting at like 5 psi, and when i reach 5-5500 rpms i'm still only boosting 5psi!

do supra's have limp modes? that's all my friends and i can come up with. one suggested that i should reset my ECU, anyone agree with that?

anyone know what the problem might be?

 

[IJ.]

Auto V's manual?

 

[Eric_Odie]

both my friend's and mine are manual.

 

[IJ.]

K that rules that out then (I believe they have different boost levels stock)

In limp it will pull timing but it can't hurt to reset the ECU then take it for a quick drive to give it time to relearn before leaning on it!

 

[Eric_Odie]

ok, i'll try that out. how much time would you prefer i give the ecu to relearn? 50 miles? just asking so i don't make any other problems appear because i didn't wait long enough or whatever...

 

[IJ.]

Don't know if there's any set time period, just cruise around the hood a bit do some stop starts and such and it should be fine.

Last time I ran on the stock ECU it ran/idled like crap for about 10 minutes then settled down.

 

[Eric_Odie]

i'll try this out tomorrow morning in Auto Shop. thanks for the help!

 

[IJ.]

No probs!

Your buds car may have been played with as well!

Once Jeff Lange see's this he can advise on how much boost each year got I recall something about the boost being raised when they changed from the 6m crank to the 7m but I'm not certain. (that happened around 89/90)

 

[mkiii222]

My 87 shows 5 psi on the stock gauge. Whether it's low rpm uphill or high rpm full throttle, it maxes out at 5.
If it's supposed to be higher I can blame an old air filter(have an HKS SMF on the way) and an 18 yo cat(need a new one by July to pass emissions anyways) for blocking the flow.

 

[aye mate]

Eric Mods?
aaronc222 I put my money on that cat. My car used to do the same thing. Even when I got a 3in. Downpipe(stock elbow) with only one cat my max boost was like 6psi. Take that cat off after emissions and I bet your boost will increase.

 

[turboa7mgte]

boost leak
Weak waistgate accuator spring
Bad gauge
Clogged cat

First check all clamps and hoses to make sure that everything is tight and hoses have no cracks or cuts.

If you are using the stock gauge then try an aftermarket.... The stock ones are know to be inaccurate.

Put a couple washers under the waistgate accuator to see if the boost increases

I took my cat off and gutted it for a free fix once.

Good luck,

 

[gixxer750]

My boost gauge goes up past 8+....like about a quarter inch above it....oh wait....nm

 

[Eric_Odie]

i'm bone stock except for HKS BOV.

checked hoses and clamps, everything is tight and not cracked or cut.

i didn't have time to reset the ECU so i didn't try that yet haha. that's probably going to be my last resort.

If i have time during autoshop tomorrow i'll check the wastegate actuator spring, and as for the cat, i can check that at home after school.

we'll see how everything goes...

 

[Jeff Lange]

I'm guessing it's probably the wastegate actuator, or your boost gauges.

The wastegate pressure line to the actuator changed positions in 89 as well (likely causing a tad higher pressure, but the stock specs are quite the range, and the range did not change between years), however, 89-92 were all the same.

Your cars should both be boosting very very closely, but a wastegate can get weak over time, my stock one had me boosting around 5psi as well, I shimmed it to get it back up to around 7.5psi, I'll be adding a boost controller as well.

 

[IJ.]

Jeff Lange= SM's SupraEncyclopedia

Thanks Jeff!