3S-GTE JDM 3rd Gen Turbo Engine car boosting too high with rebuilt turbo and 3'' exhaust

Pritch · 05-17-2009, 02:47 PM

Hello folks

after spending 3 weekends installing a rebuilt turbocharger, downpipe and custom-built exhaust onto my car (1993 mr2 turbo JDM) i take it for a ride last night...

I'm measuring boost with an AEM Tru-BOOST controller that's not presently 'controlling' anything and just acting as a gauge. (ie it's turned off)

so i go for a spin, and notice that its hitting as much as 16.3 psi (in second gear)

Note that I never had a boost gauge prior to this one, other than the factory unit.

I was planning to use my new boost controller to move up to about 15 psi, but for some reason, the car is boosting beyond that before i even turn the controller on!

im curious why it would be so far above stock, and why the factory fuel cut wouldnt kick in before that.. i was under the impression stock was 11 to 12 psi, and that the fuel cut would kick in by 16 psi.

Here are more details

Turbo: CT26 with complete rebuild and upgraded wheels (rebuild guy says about 15 percent more agressive... out of a supra??)

Intercooler: HKS replica

3'' downpipe and full 3'' mandrel exhaust

boost is measured via a "T" in the yellow boost hose at the back of the engine's intake manifold)

do you think my setup is safe at 16 psi? do you think the past owner modified something?

any advice is appreciated..i dont know if i trust my car yet....or if i just wasted $400 on a boost controller!
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mr2magic · 05-18-2009, 02:47 AM

The money was wasted less on the boost controller and more on the ct26 upgrade

There is really no point in upgrading a CT26 to anything, the numbers don't change that much and certainly not 15%. It would have been better to go CT20b or CT27.

Anyway, are you sure you installed the turbo and downpipe right? Sounds like you have a problem at the wastegate..

Maybe the downpipe interferes with the flapper cuasing the wastegate to only open partially (I think the berk downpipe had this problem!)

Pritch · 05-18-2009, 10:22 AM

im researching and that looks like a very big possibility..but the problem seems to be sort of intermittent...if its mechanically jammed...wouldnt it do it every time?

mr2magic · 05-18-2009, 02:29 PM

That depends on how big an obstruction is in the way. Remember the flapper door is not something built to nanometer tolerance

They are pretty wobbly in fact

Maybe it only catches sometimes???

My tip: remove the rod from the wastegate to the turbine housing and move the flapper by hand. Try it more than once just to make sure it doesn't catch.

As to your fuel cut not cutting in: are you sure there is no fcd installed, maybe it's only the Z-Diode mod. Check at the MAP-Sensor whether something has been modded.

What are you using to measure boost?

PearlJammzz · 05-18-2009, 02:35 PM

I was hitting over 16psi on my almost stock gen2. It was a 94 so it had the higher fuel cut, and on a hill I'd hit fuel cut in 2nd gear (at close ot sea level, now that I have the car at ~4500 feet it doesn't get closer to that). Only mods were a 2.5'' DP and exhaust.

I believe on 93+ cars the fuel cut is 16.7 or something close to there. You should be fine...can you hit 17 at all? It should for sure put you in limp mode if that happens. Go do a hard pull in 3rd gear up a steep hill and let us know

.

Pritch · 05-18-2009, 02:57 PM

hi guys

boost being measured with an aem tru boost gauge type controller. it's tee'd in just beyond the manifold on the yellow reference line. boost cut was happening around 17.5 to 18.3 psi generally. consistently happened at a peak of 18.3 most of the time.

i have just completed lubricating the wastegate rod where it comes out of the actuator with some WD40 and also DISCONNECTED the TVTS line (sorry if i spelled it wrong... its the 'second' line coming out of the wastegate actuator).

I read that this caused problems if it remained hooked up and you were trying to control boost manually. i removed the line and capped the actuator and the line. no problems now. looks like that solved it!

i went for a ride on a very 'conservative' setting with the boost controller, and the most i could make it boost was about 14.6 psi.... no sign of spike or fuel cut.

I guess i just made a silly oversight

05-17-2009, 02:47 PM	#1 (permalink)
Pritch Cage Fighter Join Date: Aug 2008 Location: Sudbury Ontario Posts: 134 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	car boosting too high with rebuilt turbo and 3'' exhaust Hello folks after spending 3 weekends installing a rebuilt turbocharger, downpipe and custom-built exhaust onto my car (1993 mr2 turbo JDM) i take it for a ride last night... I'm measuring boost with an AEM Tru-BOOST controller that's not presently 'controlling' anything and just acting as a gauge. (ie it's turned off) so i go for a spin, and notice that its hitting as much as 16.3 psi (in second gear) Note that I never had a boost gauge prior to this one, other than the factory unit. I was planning to use my new boost controller to move up to about 15 psi, but for some reason, the car is boosting beyond that before i even turn the controller on! im curious why it would be so far above stock, and why the factory fuel cut wouldnt kick in before that.. i was under the impression stock was 11 to 12 psi, and that the fuel cut would kick in by 16 psi. Here are more details Turbo: CT26 with complete rebuild and upgraded wheels (rebuild guy says about 15 percent more agressive... out of a supra??) Intercooler: HKS replica 3'' downpipe and full 3'' mandrel exhaust boost is measured via a "T" in the yellow boost hose at the back of the engine's intake manifold) do you think my setup is safe at 16 psi? do you think the past owner modified something? any advice is appreciated..i dont know if i trust my car yet....or if i just wasted $400 on a boost controller! pritch is online now Board Rules, Help with posting, Vendor Help and Rules Edit/Delete Message

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05-18-2009, 02:47 AM	#2 (permalink)
mr2magic deutsch type skillz Join Date: Feb 2008 Location: Hannover, Germany Posts: 1,201 Thanks: 107 Thanked 53 Times in 49 Posts My Google Map iTrader Rating: (3/100% )	The money was wasted less on the boost controller and more on the ct26 upgrade There is really no point in upgrading a CT26 to anything, the numbers don't change that much and certainly not 15%. It would have been better to go CT20b or CT27. Anyway, are you sure you installed the turbo and downpipe right? Sounds like you have a problem at the wastegate.. Maybe the downpipe interferes with the flapper cuasing the wastegate to only open partially (I think the berk downpipe had this problem!)

05-18-2009, 10:22 AM	#3 (permalink)
Pritch Cage Fighter Join Date: Aug 2008 Location: Sudbury Ontario Posts: 134 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	im researching and that looks like a very big possibility..but the problem seems to be sort of intermittent...if its mechanically jammed...wouldnt it do it every time?

05-18-2009, 02:29 PM	#4 (permalink)
mr2magic deutsch type skillz Join Date: Feb 2008 Location: Hannover, Germany Posts: 1,201 Thanks: 107 Thanked 53 Times in 49 Posts My Google Map iTrader Rating: (3/100% )	That depends on how big an obstruction is in the way. Remember the flapper door is not something built to nanometer tolerance They are pretty wobbly in fact Maybe it only catches sometimes??? My tip: remove the rod from the wastegate to the turbine housing and move the flapper by hand. Try it more than once just to make sure it doesn't catch. As to your fuel cut not cutting in: are you sure there is no fcd installed, maybe it's only the Z-Diode mod. Check at the MAP-Sensor whether something has been modded. What are you using to measure boost?

05-18-2009, 02:35 PM	#5 (permalink)
PearlJammzz Cage Fighter Join Date: Feb 2006 Posts: 2,115 Thanks: 9 Thanked 74 Times in 69 Posts My Google Map iTrader Rating: (7/100% )	I was hitting over 16psi on my almost stock gen2. It was a 94 so it had the higher fuel cut, and on a hill I'd hit fuel cut in 2nd gear (at close ot sea level, now that I have the car at ~4500 feet it doesn't get closer to that). Only mods were a 2.5'' DP and exhaust. I believe on 93+ cars the fuel cut is 16.7 or something close to there. You should be fine...can you hit 17 at all? It should for sure put you in limp mode if that happens. Go do a hard pull in 3rd gear up a steep hill and let us know .

05-18-2009, 02:57 PM	#6 (permalink)
Pritch Cage Fighter Join Date: Aug 2008 Location: Sudbury Ontario Posts: 134 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	hi guys boost being measured with an aem tru boost gauge type controller. it's tee'd in just beyond the manifold on the yellow reference line. boost cut was happening around 17.5 to 18.3 psi generally. consistently happened at a peak of 18.3 most of the time. i have just completed lubricating the wastegate rod where it comes out of the actuator with some WD40 and also DISCONNECTED the TVTS line (sorry if i spelled it wrong... its the 'second' line coming out of the wastegate actuator). I read that this caused problems if it remained hooked up and you were trying to control boost manually. i removed the line and capped the actuator and the line. no problems now. looks like that solved it! i went for a ride on a very 'conservative' setting with the boost controller, and the most i could make it boost was about 14.6 psi.... no sign of spike or fuel cut. I guess i just made a silly oversight