AFR mods?

[Spinnetti]

So mine just a stock engine with minimal exhaust, and I'd like to get more power out. I noticed when I pulled the plugs it looks like it runs pretty darn rich... is this typical, and if so, How do you lean it up a bit? - I'm looking to do this on little or no money btw.... I was thinking maybe a small air bleed to the intake would lean things up a bit?

thoughts? Other ideas to get more HP out of this motor at low cost?

 

[EyesofThunder]

Problem with an air bleed is it is going to be worse at lower rpms and almost unnoticeable.

You really should address it with the MAF or with the injector flow rate. Most car companies run very rich at WOT, rich is SAFE, it also keeps cat converters from melting prematurely.

But you can reduce fuel pressure some and get a nice scale across the whole rpm range.

I am a PCM Tuner for GM stuff. I haven't dug into the Lex/Toy stuff yet, but will. I can make a MAF scaler that you can do some adjusting there for some tuning, or to run dual MAF's for twin turbo applications or other twin throttle body applications.

Oh, adding exhaust mods and actually reducing backpressure will by nature lean it out some.

So mine just a stock engine with minimal exhaust, and I'd like to get more power out. I noticed when I pulled the plugs it looks like it runs pretty darn rich... is this typical, and if so, How do you lean it up a bit? - I'm looking to do this on little or no money btw.... I was thinking maybe a small air bleed to the intake would lean things up a bit?

thoughts? Other ideas to get more HP out of this motor at low cost?

 

[Spinnetti]

Well, my car is in a race series that the whole cost less safety is <$500, so fancy solutions are out. I corner weighted today, and I've got it down to 3175lb with cage and full tank of gas, but its still pig slow compared to my daily driver which only has a 1.8l engine and 3500lb! (about 4lb/hp difference)

 

[Spinnetti]

Problem with an air bleed is it is going to be worse at lower rpms and almost unnoticeable.

You really should address it with the MAF or with the injector flow rate. Most car companies run very rich at WOT, rich is SAFE, it also keeps cat converters from melting prematurely.

But you can reduce fuel pressure some and get a nice scale across the whole rpm range.

I am a PCM Tuner for GM stuff. I haven't dug into the Lex/Toy stuff yet, but will. I can make a MAF scaler that you can do some adjusting there for some tuning, or to run dual MAF's for twin turbo applications or other twin throttle body applications.

Oh, adding exhaust mods and actually reducing backpressure will by nature lean it out some.

I know this is old, but the back of my car is covered in soot. Would dead o2 sensors affect this? I only care about WOT. If I did the fuel pressure trick, how much would you suggest backing off? - 2psi increments maybe?

 

[EyesofThunder]

Dead O2's would, the ECM would see lean and try to compensate and richen the heck out of it. Doctoring up fuel pressure will only make it drive worse.

If you disconnect the O2's the ECM will fail the sensors and then go to values in the VE Tables. If you disconnect the MAF too, then it is pretty close to Alpha N on the stock ECM as you can get. But the check engine light will be on.

I would ALWAYS monitor AFR then with a wideband, you don't want it to go lean and melt a piston or burn a valve. Lean is bad, rich is safe. The gains aren't huge between them, but one will ruin your day, one will make you need to wash your rear bumper more often....

I know this is old, but the back of my car is covered in soot. Would dead o2 sensors affect this? I only care about WOT. If I did the fuel pressure trick, how much would you suggest backing off? - 2psi increments maybe?

If anyone has a stock ECM/ECU for any 90-05 RWD Lex, and wants to donate it so I can work on seeing what can be done about a real tuning solution let me know. I have the tools, but not the hardware....Not the biggest priority, but a ECM in hand goes a long way....

 

[Spinnetti]

Dead O2's would, the ECM would see lean and try to compensate and richen the heck out of it. Doctoring up fuel pressure will only make it drive worse.

If you disconnect the O2's the ECM will fail the sensors and then go to values in the VE Tables. If you disconnect the MAF too, then it is pretty close to Alpha N on the stock ECM as you can get. But the check engine light will be on.

I would ALWAYS monitor AFR then with a wideband, you don't want it to go lean and melt a piston or burn a valve. Lean is bad, rich is safe. The gains aren't huge between them, but one will ruin your day, one will make you need to wash your rear bumper more often....



If anyone has a stock ECM/ECU for any 90-05 RWD Lex, and wants to donate it so I can work on seeing what can be done about a real tuning solution let me know. I have the tools, but not the hardware....Not the biggest priority, but a ECM in hand goes a long way....

I could go get one from the junk yard I suppose.... what do you have in mind? You'd need a car on the dyno to really tell anything wouldn't you? Bit less fuel except WOT, and a couple degrees more base timing (scalar) mebbe? I don't need a zillion more hp, but my power/weight is a bit low. I'll cut some more weight off it, but can't cut more than another 50 lb or so.

My car is purely a race car, with all cats removed and the exhaust chopped off after the pre-mufflers. I may replace those with a couple of resonators too.

My Bosch understanding is that o2 goes open loop quickly off idle, so even dead o2 should make no difference on a race car right?

 

[brawls43]

Don't you get CEL when you pull the O2 sensors? I had a dead one throw a code, we replaced it. We're still running the cats based on input from the forum. But nothing else. I have a spare ECM I could potentially donate if that lets EyesofThunder see if he can get into the ECM and adjust any tables. Advancing timing a little would be nice.

 

[Spinnetti]

Don't you get CEL when you pull the O2 sensors? I had a dead one throw a code, we replaced it. We're still running the cats based on input from the forum. But nothing else. I have a spare ECM I could potentially donate if that lets EyesofThunder see if he can get into the ECM and adjust any tables. Advancing timing a little would be nice.

Beats me, never checked. I pulled all three cats and the rear "tattletale" sensors. It's not odbii, so never checked for any codes. So you use your cats as mufflers? Do you see any soot? I'm doing this pure lemons style - haven't touched the 250k mile motor other than plugs, a belt and oil changes and removing parts of it.

 

[brawls43]

Beats me, never checked. I pulled all three cats and the rear "tattletale" sensors. It's not odbii, so never checked for any codes. So you use your cats as mufflers? Do you see any soot? I'm doing this pure lemons style - haven't touched the 250k mile motor other than plugs, a belt and oil changes and removing parts of it.

Yeah, we had been running a glasspack for a muffler, but it was so quiet, we got rid of it too. We left everything in front of the stock merge y-pipe location, so both cats and all 4 O2 sensors. We're still fairly quiet at full throttle. We're also all stock on the engine, minus the EGR delete. But that was just ditching parts. We get so much condensation out of the exhaust at idle, its crazy. Had the catalysts off this winter and they look pristine. Granted we've only 140k on our motor.

 

[Spinnetti]

Yeah, we had been running a glasspack for a muffler, but it was so quiet, we got rid of it too. We left everything in front of the stock merge y-pipe location, so both cats and all 4 O2 sensors. We're still fairly quiet at full throttle. We're also all stock on the engine, minus the EGR delete. But that was just ditching parts. We get so much condensation out of the exhaust at idle, its crazy. Had the catalysts off this winter and they look pristine. Granted we've only 140k on our motor.

Cool. Although it works just fine now, I was thinking of ditching the pre-mufflers, throwing on a couple glasspacks and sending the exhaust out the sides... might be asking for problems I don't have now though?