The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support STM Tuned
Please Support Fuel Injector Clinic

lean with 660s?

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

boosted1stgen

Proven Member
66
0
Jul 27, 2013
Kingman, Arizona
Alright just need some opinions, car has 1200 miles on fresh rebuild. Seems to run fine except when i get into upper rpms in boost kinda cuts out. But still goes to redline. Data logger shows some knock, sometimes as high as 20ish counts. The wierd part is itll still have 21 give or take degrees of timing advance, and the egt gauge ususlly never goes past 1500 ever. Ive tried richening it up some but didnt seem to affect it. The reason i was thinking it might be lean is the knock off 255 fuel pump, cause one night on pump gas boost controller set wuld hit 15-16. Then i put ssome 100 octane in and get on it to do a log and boost now hits 18 without me adjustying anything. What you guys think? The low egts are throwing me off.
 
I see that you have a EGT sensor but do you have a Wideband? This could be used as a checks and balances to make sure the EGT is at least reasonable.

With that much knock, your ECU should be pulling about 7 degrees of timing, so something must be off there. 3 counts of knock should pull about 1 degree of timing so unless you are running 28degrees of timing under load (what im assuming you consider upper RPM’s), the ecu is not reacting to the knock like it should.
 
Unfortunatelty i do not have a wideband yet, for what its worth the o2 readout on logger sits around .85 volts at WOT. Could a faulty cas cause the ecu to not respond to knock appropriately? And also does the adding of 100 octane causing boost to increase all by itself indicate that its a fuel delivery issue?
 
That narrowband 02 is only going to be accurate around Stoich (14.7:1) and not accurate past a point or so leaner or richer. Its job is to keep closed loop operation happy when trying to reach stoich AFR’s. It was never intended to be used past that point.

Adding 100 octane fuel in itself should not raise the boost. However, boost can change based on ambient air temp (colder equals more boost), load plays a role and many other little factors.

A fuel system does not care for the octane rating of a fuel. Since 93 and 100 octane have about the same density and flow characteristics, the fuel system should react the same.

When this 100octane was ran, did your knock decrease?

I would not continue to run the car with that much knock. Turn down the boost until you find out what is going on.
 
The day i put the 100 octane in was a day before i recieved the cradle for palm, so i wasnt able to log, yea i havent been driving it much till i figure it out. Also when i measured head before i put it on, i think the machine shop ended up taking almost 40 thousandths off the head(alot i know). Could that raise compression enough to be a problem?

Also my safc setting for hi is only around -15ish. If thathelps. And my supra pump went bad, and could only afford a knock off 255 at the moment which has rewire.
 
Last edited:
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top