plenum/ throttle bodyand a/f ratio?

03redfiregt · Feb 14, 2004

I have been thinking about getting the c/L plenum with a 70 or 75mm throttle body. Does anybody know about how much these two lean out the a/f ratio? I have a superchips microtuner installed in my car so the fuel curves are'nt stock. I'm not sure if these will make me too lean. My only other change on the intake side is a denscharger to the maf.

XStanger · Feb 14, 2004

03redfiregt said:
I have been thinking about getting the c/L plenum with a 70 or 75mm throttle body. Does anybody know about how much these two lean out the a/f ratio? I have a superchips microtuner installed in my car so the fuel curves are'nt stock. I'm not sure if these will make me too lean. My only other change on the intake side is a denscharger to the maf.

At a local dyno the other night, there was a guy with the c/l plenum/tb/mass air/ inlet tube and his a/f was actually way too high. I think it was in the high 14's and low 15's before his tune. From what the dyno guy said, it was more the maf meter, and not the plenum t/b.

Sam98 · Feb 14, 2004

03redfiregt said:
I have been thinking about getting the c/L plenum with a 70 or 75mm throttle body. Does anybody know about how much these two lean out the a/f ratio? I have a superchips microtuner installed in my car so the fuel curves are'nt stock. I'm not sure if these will make me too lean. My only other change on the intake side is a denscharger to the maf.

They shouldn't lean it out at all, because no matter how much air you let in, it is still metered by the MAF and the MAF voltage is what the PCM uses to determine how much fuel you need. If there is a difference it will only be until the adaptive strategy has corrected the long term fuel trims.

Morgstang · Feb 14, 2004

XStanger said:
At a local dyno the other night, there was a guy with the c/l plenum/tb/mass air/ inlet tube and his a/f was actually way too high. I think it was in the high 14's and low 15's before his tune. From what the dyno guy said, it was more the maf meter, and not the plenum t/b.

I had the same problem with mine. When we originally made a dyno run the a/f was at 18. Scared the tuner to death. He had to make numerous changes to the MAF to finally get it to a comfortable a/f ratio. I had the MAF changed because of a problem with it also. If anyone has any idea why it would still be so lean even after changing the MAF, please let me know. The tuner has since fixed the a/f ratio but we still wonder why it would have been so high to start with.

2000GT · Feb 14, 2004

The C&L plenum and TB combo will lean out the a/f ratio a bit more - 0.2-0.4.

I asked Lee Bender of C&L and that's what he told me. Unless you car is already on the verge of detonation, this minor change doesn't sound like it's anything to be concerned about.

hognutz · Feb 14, 2004

if you are just doing the plenum tb make sure you get the 75mmtb(flows more air with the 75) and the car should learn it just fine. don't buy the pos c&l maf and you will be fine. most people have problems because they "upgrade" thier maf when they don't need it and that is an added variable.

bennyjammin · Feb 14, 2004

The plenum/tb combo leaned me out considerably and was easily noticed, without ever putting my car on a dyno. When I programmed my ECU with the Superchips, I was unable to use the performance setting because I was pinging really bad, and this is with 91 octane. To solve this, I bought the Pro-M remote optimizer and richened it up by calibrating the MAF. Now, the engine runs smoother and I am able to use the performance setting. I still don't know if I'm at a perfect a/f ratio, and won't know until I put it on a dyno with a a/f meter. But hey, at least now it's not pinging. BTW, the car feels much faster now, even before I put the performance setting on. I think I was so lean that I was actually losing power.

BlackVert · Feb 28, 2004

I just installed the MAF kit, True-Flow Pipe, TB, and Plenum. It started pinging bad under load but, then after disconnecting the battery for an hour, the pinging has stopped. I still have a check engine light and the idle is wierd (kind of like it was when the IAC needed to be replaced). Could a lean A/F ratio cause the check engine light, or is it more likely that the TPS is off and needs to be adjusted?

BTW, my "before" dyno showed I was fine low end but rich on the high end, for what that is worth. I haven't done the "after" dyno yet.

plenum/ throttle bodyand a/f ratio?

03redfiregt

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Morgstang

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2000GT

hognutz

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