has anyone had an A/F gauge on an Evo with a MBC set to 19~20 psi and no AFC or re-map. im curious to how much the additional boost is leaning it out. if its leaning it out some i dont understand why id need a SAFC. also has anyone logged the car at 19~20 psi to know if its pulling timing and how much? thanks for the help

 

 

THe engine runs really rich at WOT, Some have speculated that the maps may have been originally intended for either higher boost, or a maintained stable boost through redline.. This is just rumor. I "Should" have most of my instrumentation installed (A/F gauge, and EGT probe) by next week, and I"m willing to experiment a little.. If I discover anything I'll certainly post it.

 

I have.
a/f ratio at 19, up to 21psi all the way through redline is like this. Car runs rich throughout, in the high 10:1 range, up to about 4800rpms or so. At 5000rpms, the ECU starts to dump fuel. By 6000rpm or so, it's running really rich (low 10:1 range). Before 6500rpm to redline, the car runs about 9.5:1 ratio, which is insanely rich. The wideband O2 we used only went as low as 10:1, and the graph dropped below that line.

In theory, I'm guessing you can boost the hell out of the car, and eventually it'll max out the injectors trying to run rich, but be lean because of the added boost, but it's not accurate. Let me know what happens if you do decide on trying it.

 

I think I read in some FAQ or something, but isn't dumping fuel like this intended to prevent pre-detonation ( knock ). Sounds weird but I think i read that it is referred to as charge cooling ??

But if Mitsu is dumping fuel like this, what does it do to emissions ? Surely some fuel will go un burnt raising the hydro carbon count ??

 

Let me know how all goes...I planned on doing the same thing if an SAFC is not needed!

 

Ive heard people are running 21+psi and LEANING out the upper RPM range too.

9.5:1 is insanely rich. Youd want that at LEAST 10.5 or even 11:1 for max performance.

I saw Pruven Performance's dyno graph and theyre were running like 12:1, that is high, but shouldnt be driven all the time like that i assume... although many DSM guys tune their cars around 12:1 or 12.5:1...

 

12.1 is about as lean you wanna go for daily driving-dont have to mess with it - wont dentonate on bad gas - damn its cold outside conditions.

 

Hey Joe, where are you at in Atlanta? I'm getting my gauges done this weekend, I'm going with your information and mounting the EGT gauge in the DP near the blower to measure TOT. I'd like to meet up and compare readings with your car. I'm still stock, but will order some parts soon

Manuel

 

Manny,

I'm up in Alpharetta off Haynes Bridge. My EVO is stock as well - I'd like to see what your temps are as well and compute the temp diff.. I'm in Chi-town this week but I'll be home this weekend.

What mods do you have planned?

 

I've seen an Evo running 19psi to redline with an afc set at -15 on top and the a/f was still below 11.0. My afc was set at -14 on top and the a/f was in the 11.5 range but that was on stock boost. I'm now running 1.4 bar to redline and set the afc to -11 on top and was running 106mph trap speeds at the track. So to answer your question I think the added boost does lean it out a tad but not much.

 

There really is no way to accurately define the ideal A/F, as everyone uses something different to measure. if you are using a "blinkey blinkey" A/F meter, a GReddy A/F gauge, Tomei A/F gauge, Field, etc., it will be reading leaner than the actual mixture because it uses a narrow band 02 sensor. Some people use the later GM sensors, which we like to call quasi wide bands, as they read from 0-5 volts, so are much more accurate than standard 02 sensors, but still tend to loose it below 12.0:1 and above 15.5:1.

True widebands, like the FJO, Horiba, Motec, and the like, are very accurate and stable down to around 9.5:1 and up to around 17:1, so they give w nice wie span, and are accurate within that span.

For street driving, err on the side of richness....better to be safe than sorry.

Adam

 

Anybody come up with figures yet on just getting a MBC or EBC as far as EGT and AF Ratio? I also wanted to get an MBC possibly w/o a S-AFC for now, if the ECU will compensate for the fuel needed for the boost increase.

 

Because of how rich the engine runs, you probably could run an MBC at about 19-20 psi to redline without an AFC.. but you really aren't going to take advantage of all the extra power thats left in there without tuning the fuel curve a little... I'm a bit unsure that I even want to instally my MBC at this point because I'd prefer to have control over the stock solenoid to control boost.. Its just alot more stealthy and less likely to raise eyebrows at the dealer. Not to mention you can more easily reverse the modifications.

I wonder if I could create an intercepter device for the stock solenoid to do two things.. To set the duty cycle of the solenoid (assuming it really is duty cycle based) and to trick the computer into thinking the solenoid is still connected, and even offer a hybrid control.. (adjustable boost levels to tweak the stock controllers settings)

This however may all be a moot point because of the Xede unit will have boost control, Works will have a remapped ECU with optimized boost curves, and there will probably be several standalone replacement ECU's with boost control built in.

 

i have the boost set between 19 and 20 psi and it seems to run fine. it pulls a lot harder now because its not dropping boost. i talked to some other people and they all agreed that three more pounds of boost should be fine above 5 grand, because its soo damn rich anyway. i only run 93 octane though so i dont know if the car would be fine with anything less. i was planning on just trying it and then hooking the stock ebc back up but i think ill leave it. once you gain the power its hard to go back.