I finally got a new ECU (Rtek stage 2) for the S4 GXL, and before i start making changes to stuff i want to make sure i know what i'm getting into.

Any recommended reading for tuning an NA rotary? Almost everything with any kind of detail i've found so far has been turbo specific. Most of what i'm seeing for the NA cars is "Lean it out until it pings then add just a bit of fuel back".

Ideas? Suggestions?

 

Don't tune without a wideband. Data logging wideband, some good hard pulls on the street and you can start tuning that way. Don't remove fuel till it pings. Thats just being unsafe. I hear that too.

 

Yea, pings are bad in a rotary. Or so I have heard.

Rotary engines don't take well to detonation like piston engines do. Because a lot of times when there is detonation it destroys one of the apex seals.

Wideband or a dyno...

 

lol awsome hatch pic, i laughed my *** off when i saw that light for the first time,

 

To be fair, pinging on a NA isn't nearly as bad as with a turbo. I ran mine for maybe a 1/2 mile with the timing royally fucked up and it was pinging BAD. Nothing happened.
This is not so say that pinging isn't bad because it is, I'm just saying that maybe on an NA its not AS bad. Generally the best way to tune a rotary is to tune the AFR's using a wideband as suggested.

 

I never even looked at my hatch light to see if thats what it looks like. Im going to have to go look now.

 

I'm not familiar with the RTek so I don't know how much control it gives you...You'll need a wideband to tune AFRs, EGT to tune timing (well you can tune it all with EGT but I prefer the wideband).

Start rich and lean it out until you stop making power. You'll find this somewhere around 12.5:1 or so for most NAs.

If you have timing control, you can try bumping timing a few degrees. You can be fairly aggressive under high vacuum but don't go nuts under high load. You won't make as much power with timing as you think. 20 degrees at WOT is about the maximum that's going to help. If EGTs go up sharply, then back down.

The engine will handle some detonation as long as you don't go nuts with the timing.

 

Cool thanks a lot for the info! A WBO2 sensor is already on the shopping list. The Rtek stage 2 gives you loads of control over both fuel and timing as well as 2 loggable inputs, so that's not an issue.

Any recommendations for the wideband / EGT sensors? Most i've been able to find have been in the $300-$400 range (that's near what i paid for the ECU!) I don't need a lot of built in features, just a linear 5v output, since the ECU can log it.

 

Really, can you explain a little more about using EGT to tune timing?

 

I currently am running just an SAFCII for fuel correction and a Zeitronix ZT-2 wideband ($279 USD). another cheaper option for wideband if your ECU can datalog is the Innovate LC1 ($199 USD) http://www.innovatemotorsports.com/products/lc1.php

in my case the stock ECU + SAFC is a bit limiting in terms of tuning, but i basically did street tuning and adjusting fuel based on the datalogs. i aimed for about a 12.5:1 AFR across the range at full throttle, but more power might be made slightly leaner at 13.0:1 but it's hard to say without a dyno. the main thing is to have a consistent AFR across the rpm range and to not be too rich or too lean.

please be cautious when tuning, however i can tell you that if your timing is properly set (to stock) there is very little risk when it comes to NAs.
i have accidentally tuned too lean a few times for full-throttle pulls and nothing bad came of it, other than a noticeable loss in power.

for cruise (low-throttle) tuning you can lean it out as much as you want. 15.0:1 AFRs seem to work good for me, and saves me a decent amount of gas on the highway.

 

AEM UEGO is often cheap at places like RX-7 Store. The LC is also under $200 as I recall.

It's really hard to see problems caused by timing changes via an A/F gauge. You may notice slight momentary lean spots during detonation but you really have to be watching for that. With an EGT gauge, you can see the temps skyrocket when you go to far with timing advance.