I was able to get ahold of a motec WB o2 and would like to start tuning my car on the street. I have an e6k running a 90 TII engine on a base map from the hitman. I would like to know what AFR I should be running with 91 octane pump gas under boost and while crusing. This car is going to be driven sevral times a week so its more important to me to have it tuned a little conservative then for all out power. I have searched on this and 11.5-11.8 seem to be what most say is safe under boost (I hope) but I cant find much on the crusing AFR. Right now hitmans map seems to work really well under boost no misfires or pinging (I have not installed the WB yet) but I want to start tuning for crusing first. I was told that it is better to lean out the light load parts of the map than to use closed loop. Ive read elsewhere that tuning for crusing should be done leaner than 14.7 is this true or will it damage my motor? Also about the timing maps should I mess with them or just leave it alone?

 

Rotaries like to run rich. Even at idle the car is not going to run at 14.7:1, more like 13.7:1 (IIRC). Start there and work you way towards full boost (15psi??), and have the a/f around 11-11.5:1. There is a thread about tuning in the ECU section. It gives some info on a/f and such that will help you out.

 

About a year ago I remember Hitman posting that you should run
11.5 no leaner under boost (probably up to 15psi)
12.6 at idle
13.8-14.5 at cruise

 

you will find that with the closed loop off your off boost ratios will be around 12.5-13.5, get your mixtures in that area, then tune you closed loop so that after a short period of steady state cruise the, closed loop pops on and gives you a flick over voltage of 450 mv on the o2, the wideband will then read about 14.7 and will occasionally get up to 15:1, with closed loop tuned properly, what you save in fuel will pay for you wideband, I am around 28-30 mpg highway now, which is better than what the TII got stock, in fact its better than what the N/a got stock..
right now my closed loop is 450 mv target, 26% throttle cut off with a 2200 rpm limit..Max

 

2200 rpm limit? Isn't that kind of low? what's your speed at 2200rpm?

 

Thanks guys that does help those were the responses I was looking for that will help me out a lot. What about the timing maps though? I was thinking I should just leave them alone because I really dont know what im doing yet.

 

If you are not shooting for max power then you should just leave your timing maps alone. You can get quicker spoolup and add a few HP up top by playing with the timing maps.

 

Setzep, I like to just throw the car into 5th as much as I can and let it bomb along, some of our roads here are long straight stretches with speed limits that are pretty low, so the sooner I get into closed loop the better. I pulled 28-30 mpg with my TII this weekend which is better than that car ever got new, or stock, the wideband o2 will pay for itself in the fuel it saves..Max

 

Those are some impressive #'s! My 1.8 integra gets that driving to work everyday on the highway. Does the engine "chug" or "buck" while running that low of afr? What is your EGT while crusing?

 

i need to do that with the 20b, i'm getting almost 11mpg right now

mike

 

Yeah, lean the cruising areas as lean as you can before it starts to surge.&nbsp Also, keep an eye on the EGT's as we try to keep it under 900C.


-Ted

 

Do you have the egt before or after the turbo?

 

Setzep, the 13b will start to buck around 15.9-16.5:1, other that its plenty smooth.
I have resisted even getting involved in egt's at this point in time, there are so many variables in changing the egt's, I really think you can lead yourself down the garden path with them, especially in search of the "magic ignition timing" amount. Charge air temp, fuel mixture, boost pressure, ignition timing, exhaust backpressure etc etc all affect egt so much, its hard to tell where to start,it has more tuning relevance on diesel motors where the fueling is directly tied to the timing, and fixed with a cam, in a fixed amount.
When it comes to fueling, its a bell curve in egt's, yes more fuel will cool the egt's to the point though when the excess fuel starts to combust in the exhaust manifold or turbine, egt's will start to rise again on an egt meter.
Guys that are pushing 110 deg celsius air down the throats of their motors are going to see alot higher egt's than I will, my motor does not see air over 35 deg celsius even on boost at 15 psi, so I can't ever just follow the numbers of past tuning attempts, and say well my egt's are 1400 his are 2200, I guess I need less timing or less fuel in comparison. In real terms I need more fuel as my intake charge is more dense, although the lower egt's would probably push more people to lean it out some.
Its interesting tuning a street car for mileage and power, the profile of the maps has taken on a rather agressive climb from about 4" of hg vacuum and up, if we could accurately plot a boost curve down to the specific lb/s hr, we could probably pre-map any turbo combo, or give the numbers and injector sizes to a computer and have it pre-build baseline maps. But another thing is coming to mind, being that we are sticking to a rather static rate of climb in the maps in one rpm band, it may be the actual boost curve, or the changing of the boost curve that leads to blown motors on piggybacked/stock ecu's rather than the actual amount of boost..Food for thought anyway..Max

 

Max, I'm never dissatisfied with your responces. Good post!
Back to the 2200 rpm limit you have set for your closed loop, why 2200? Why not higher so you can still get that good fuel economy while cruzing down the freeway at 75mph? Or do you have your maps good in that range anyways? Also do you or anyone know what temperature the tips of the turbine wheel start to melt off? My buddy just got a "Power Programer" for his ford powerstroke and it had two settings, 60hp and 80hp. On the 80 hp setting it says you need to watch your egt and make sure it doesn't get above a certian amount, it also goes on to tell you that if you go higher than 1300 F the tips of the turbine wheel will start to melt off.

 

Interesting, now where can one acquire a wideband o2 suitable for tuning?

I think this would make a nice tool for my garage.

 

The 2200 rpm is bottom cut off for the closed loop, I find the that below 2200 or so, the closed loop does start to play havoc with the throttle tip in, and makes high gear/low rpm operation a bit to finicky. The upper range is terminated by throttle position, 26-28% or so seems to be optimum.
I have been collecting as much turbo literature as I can, from what I can gather the turbine wheels should be good to 2500 deg f +, maybe a bit higher, Flying engine parts and other impacts seems to be the greatest threat to the turbine wheel. 1300 deg is the magic smoke limit of diesel, if your exhaust goes clear, it means you don't have enoug fuel, if I remember right.
I have had the oppertunity to look at some torn down diesel engines, it seems the exhaust valves and seats seem to take a beating from jacked up performance, the resulting turbine failures I would think are from peices of the exhaust valves coming down the line. Alot of the diesel performance kits, concentrate on fuel timing and fuel timing only, which is just as critical in a diesel or even more so than gas engines, inject to early and the piston fights the early combustion on the compression stroke, to late and the fuel burns on the exhaust stroke, probably burning out the exhaust valves at the same time.
Mike P-28: www.fjoinc.com thats where I got mine, I keep it permanently installed in the TII..Max

 

Oh ok I thought you were saying that you have it turn off at 2200 not on, makes sence now. So technically you could probably go 100+ mph while still in closed loop while still under 26% throttle, neat.
I guess they might have been refering to the diesel engine life it's self not the turbo when talking about egt temps.

Thanks again max!

-Cam

 

I just installed my haltech and I'm not to sure how it should be running. I have DEFI gauges for boost and A/F. My A/F goes from 17 to 10. I'm not sure whish side id lean or what is safe to run. I assume that the numbers that you guys are talking about are the same ones on my gauge, I'm just not sure.

 

ok i've been playing with the 20b some and i've gone from 11mpg to 15. 2200 seems to be the magic number on a t2 its about 40-50mph in 5th (no tach yet), and it takes about 18-20% throttle to just go 65-70, i had to bump mine up too. i'm looking to get another 2mpg out of the thing , it make the difference of a gas stop going to sevenstock

mike