ska3260

iTrader: (1)

scathcart, you are talking about tuning on a dyno right? using the output readings as torque and horsepower?

scathcart

Effectively, yes, but you can get close to that in street tuning if you know how to read your datalogs and how torque and power affect rate of change of engine rotational speed...

Usually when tuning an N/A, I can get to maximum power on the street, and then confirm it on the dyno. A turbo engine I will always street-tune the same way, and then usually pick up some mild extra mid-range power gains on the dyno.

For street tuning, I datalog both wideband AFR's and EGT's straight to a dedicated laptop. Peak power tends to occur right around 1550-1600 degrees at WOT on an N/A, with timing spot-on.

MARTIN

street tune first(wideband) and then tune timing on dyno...

scathcart

Cruise: constant speed, on the freeway, 60-70 mph. Typically around 1/4 throttle, 2800-3000 rpm. I use extremely lean air-fuel ratios meant to keep the combustion chamber clean and maximize fuel economy. Premixing is 80-100:1, depending on the engine, and I typicaly am developing 32-36 mpg with a standalone. The EGT's skyrocket under this kind of tuning, which some find concern with the extra stress that may or may not be applied to the internals to the engine. I tend to highly focus on the rotor cooling and supplying ample oiling when building my engines, dunno if it has any effect on it, but so far, engine longevity has been fantastic.

WOT: Wide open throttle. This is when the gas pedal is floored, foot to the floor. Maximum acceleration, maximum engine load. Requires the richest AFR's and much retarded timing to prevent detonation, and the engine from eating itself.
When the turbo is spooling, and in vacuum maps, I run around 13.5:1 AFR's. No reason to run so rich down there if the engine isn't seeing boost. When boost comes on, I quickly increase the amount of fuel going into the engine, to slow down the burn to prevent knock, hence the richer AFRS (lower numerically). I continue richening it up until peak power is made... I have my reasons for doing this.

It might be noted by some that I tune "lean", both for N/A and Turbo applications. Typical full boost AFR's tend to range in the 10.5:1-11.5:1 area. Longevity doesn't seem to be a problem, even with 94 octane pump gas (on the turbo engines), while running the leaner AFR's of 12.0-12.5:1, and I am not the only one stating so. There is more to detonation than simply an air-fuel ratio, and I like to try work on those areas as opposed to injecting extra fuel to combat an existing problem and costing myself some power.



Now, then, [b]do I think these values work well for everyone? No.[b/] Plug those turbo values into your stock TMIC, 550cc/min injector, 14psi stock turbo'd TII, and you'll blow your engine... They are merely reference values to go by.

I don't tned to tune with S-AFC's. On an N/A, I'd probably stick to the values I gave, but with a TII running the stock TMIC, and stock turbo, I'd lower my in-boost AFR's to the 11.5:1 area.



So, I guess for all the plug and play kiddies out there with there s-AFC's and LM-1's...
NA:
low throttle: below 1800 rpm, tune for 13.4. Above that, tune for 15.5:1.
High throttle: tune for 13.6:1.

Turbo:
low throttle. Below 1800 rpm, tune for 13.4. Above that, tune for 15.5:1.
High throttle (taken from boost reference at 0 psi): tune for 11.2:1.

ska3260

iTrader: (1)

Quote from Scathcart-
"So, I guess for all the plug and play kiddies out there with there s-AFC's and LM-1's...
NA:
low throttle: below 1800 rpm, tune for 13.4. Above that, tune for 15.5:1.
High throttle: tune for 13.6:1.

Turbo:
low throttle. Below 1800 rpm, tune for 13.4. Above that, tune for 15.5:1.
High throttle (taken from boost reference at 0 psi): tune for 11.2:1."




I really hope you are talking about a unmodded engine. Even a open element air filter will change those numbers. Like i said before my NA ran the best at 11.5 high throttle.

88rxn/a

iTrader: (6)

ok, thanks alot this helps alot, 1 more q. im throwing a turbo on my n/a(s4 turbo) and running 550 primaries and 720 secondaries with a fd fuel pump and with a tmic converted to a fmic, do you think if i shoot for these #'s^ i should be ok? i plan on shooting for 8-10lbs.?? thanks so much for the help, oh yeah and im one of those plug-n-play kiddies with a s-afc.

scathcart

Those tuning values are a general rule for streetable rotaries.... streetported or stockport No n/a will make maximum power at 11.5:1 AFR's... that's even too rich for turbo's. If you really think maximum power occurs at 11.5:1... then you really have no experience when it comes to tuning these engines.
Should I even bother asking what your timing map looked like? How about changes in power or changes in vehicle acceleration? What were your WOT EGT's like?

Didn't think so.

scathcart

Running the stock ECU, aim for 11.0:1 at ful boost under WOT at 10 psi, and make sure your timing is spot-on.

88rxn/a

iTrader: (6)

thanks!! i thought we were supposed to retard the timing a couple of degrees?for a n/a with a turbo?