MR2 Owners Club Forum banner

1 - 20 of 29 Posts

·
Re-Energized MR2 Owner
Joined
·
834 Posts
Discussion Starter #1
Just thought I'd post this for all Gen 4 owners to see.

Mods:
Gen 4 3SGTE (Installed by Prime Performance)
Intake
Intercooler
3"Downpipe
TCS 85mm exhaust
Walbro 255 fuel pump
EBC @ 16PSI
Precision 5558 turbo with Tial Wastegate

Air/Fuel ratios looked great, only hitting 11.05 while under full throttle @ 16PSI. Full boost by 4500rpm, not sure how this stacks up with other turbos, so if anyone with experience can comment, it would be appreciated. This pull was done on a 93 degree day with 22% humidity. Overall, I am happy with the numbers and the new turbo.

 

·
Premium Member
Joined
·
834 Posts
Looks good. How does it drive? What size turbine housing are you running? Alot depends on your goals for the turbo. Its pretty oversized for the current boost you're running. If you were after 350whp then a smaller faster spooling turbo would be better. If 500whp is your goal then I think you picked the right turbo.
 

·
Re-Energized MR2 Owner
Joined
·
834 Posts
Discussion Starter #3
I bought it for future goals. I wanted something I could pick up a decent amount of power while still on stock fuel and ECU.

Drives very well, I even get better gas mileage because of the slight increase in lag.
 

·
Don't mess with Texas
Joined
·
19,880 Posts
Like said above for a future goal of 500whp+ that is a good turbo and dyno is pretty good.

If on the other hand it would be staying at this power level I was spooling 700rpm faster and making almost the same power with my S252 on a 3rd gen.

Very smooth powerband, must be that 4th gen electronics.
 

·
Don't mess with Texas
Joined
·
19,880 Posts
I would go down a pound or two on the boost to give you some injector room.... But it looks good though for pretty much a stock deal.

Angel
Nah, he is fine. I ran my car at that power level for a year without a single issue. Fuel cut kicks in before you can really outpace the fuel system.
 

·
Don't mess with Texas
Joined
·
19,880 Posts
I am under the impression 11.5 AFRs is about the extent you want to push it. At 11.05, I feel pretty safe.
Correct, even up to 12.0 is not bad but I would not want to run it there all the time. You have enough wiggle room that should something happen and you overboost the fuel cut should keep any damage at bay.
 

·
Re-Energized MR2 Owner
Joined
·
834 Posts
Discussion Starter #11
Texas, my hose came off the bottom port of my wastegate yesterday and I over boosted into fuel cut. But why? Shouldn't it have only boosted at the wastegate spring pressure?
 

·
Don't mess with Texas
Joined
·
19,880 Posts
Texas, my hose came off the bottom port of my wastegate yesterday and I over boosted into fuel cut. But why? Shouldn't it have only boosted at the wastegate spring pressure?
Without the boost line in place the wastegate will in theory never open. In the real world they are not 100% sealed though so they do open eventually.
 

·
Registered
Joined
·
695 Posts
They will still open if you surpassed the spring pressure in the wastegate.
l
incorrect. how will it know what boost pressure it is, exhaust gas alone will not push open the wastegate. Thats not how a wastegate works.

boost reference pushes on the diaphragm which compresses the spring, without a boost reference the spring will never compress by exhaust gas pressure alone. therefor the wastegate will stay shut, causing the turbo to boost until boostcut/fuelcut.

 

·
Registered
Joined
·
701 Posts
If there is a high exhaust manifold pressure, yes, the wastegate can open even without any boost reference hose.

If the srping pressure is pretty low and the turbine housing is tiny (more exhaust pressure), then this case can happen quite easily.

This is why wastegates have a top port. This port is used add pressure to the already installed spring so that the wastegate can fight the exhaust pressure that act against the valve seat. You usually use the top port when you are running high boost pressure and low spring pressure with a small turbo.

Sam
 

·
Don't mess with Texas
Joined
·
19,880 Posts
I know every time I had a wastegate line come off my boost would spike to fuel cut without fail. Be it the stock 20b or the S252.
 
1 - 20 of 29 Posts
Top