machinehead

Ok, I know there are alot of diy tuners out there and there are many of us that have access to a wideband for setting up a/f ratios. This is relatively easy with proper tools. You have a reading, it shows 10.5 or whatever and you want 11.5 so you remove some fuel. What is not easy is knowing what is acceptable to run your timing at.
I am looking for a general guidline. Working with pump gas, which is 91 octane here, a street ported 13b, TO4S turbo with all the regular upgrades.
So what would be ok?
At 10psi?
15psi?
17psi?
20psi with 100 octane?


I know these are general statements but I am just looking for a general giude if that's even possible. I know there are many things to consider, like 15 psi at 5000rpm and 15 psi at 8000 rpm obviously could bennifit from different timing advance so I could be asking too much. I just thought I'd put it out there and see what everyone considers safe because i don't know. I have seen people recomend as much as 25 deg at 17 psi at 7000rpm. Is this realistic or just asking for trouble?
Thanks,
Cliff

relvinnian

This is just my opinion, and what I've read from what I consider to be reliable sources. Things to consider: Timing is reliant alot on extent of porting, and VE% (tq). At peak torque the timing should be at it's least advanced, anything beyond peak torque where VE% drops it can be raised or lowered liberally. It makes sense, max VE is when your motor is breathing it's most per revolution, chamber pressure and velocity are highest. From what I can tell timing should not change much at all with boost. If you can't run the boost without detonating you need higher octane, lower AITs, water injection, whatever. With higher octane you can get away with more advance, and vise versa.

Common street port MAX advance would be 15-16 deg. I might run 14 deg considering only 91 octane fuel. Any comments welcome on this.

Huge port motor would see from 10-13 deg advance, as chamber pressure/VE% is higher @ tq peak.

Playing around with timing is BAD if you don't know what you're doing. It's best to have a base map and work from there. Once A/F ratio is consistant, you can play with timing via EGT guage, and seeing how the motor respondes to more advance. This is dangerous though, and I personally would not do it without a very sensitive EGT, and knock monitor.

On an engine dyno where you could see a VE% curve would be the optimum place to tune. Tq curve is your best indication though. Be liberal.

-Brian

machinehead

Thanks, that sounds like good advice. I was pulling hard in 3rd gear last night and I heard like one loud click, It was not a missfire it sounded more like a single ping so I am going to back off of the timing. It was not at or near the rev limit, more like 6000rpm, it just happened once and that was it Maybe 6000 is my peak torque?

The_HITman

I would suggest anyone who says to run 25 degree anywhere but off-boost needs to be slapped. I would go as far as to say to not run more than around 10 degrees on 15psi on pump fuel. Ihave found rotary engines don't respond to timing in the way piston engines do. They have quite a broad window where adding timing does not add power, yet it does contribute to bringing on detonation. Seeing as you are running relatively low grade fuel you should start with quite conservative timing and slowly add one or two degrees. If you hear detonation at all back off the throttle immediately and reduce the timing by 2 or 3 degrees.

Anthony Rodrigues

You line them up and I will slap them, 10deg may be where to end up at. If the mixtures are not fairly close, listen to the last post or you will definitely loose an engine. Ask him or any Rotary tuner how they know! You do not usually get to hear a turbo rotor ping on 15 psi and a TO4. They just stop. Ask me how I know that one!
Regards-Anthony

machinehead

Thanks again for the advice, I have already adjusted my timing maps and to be honest my butt dyno can not tell the difference. I have some experience with boingers but this was and is my 1st rotary powered car so it has been all new for me. I pretty much set my maps up like I was running a distributor I gave a little extra at light throttle and dropped it down as the load rises to 10 deg at 15 psi with a split of 10.
Thanks,
Cliff

RICE RACING

Each and EVERY engine combination is different to some degree, my road going rx7 is very sensitive to timing changes in that if I have just 3 deg less timing at WOT I notice quite a drop in power, again this has a lot to do with the porting/general configuration of the engine combination (we are talking single turbos here)

It sounds like an excuse but there are many variables to consider, not the least fuel quality issues.

I would say the maximum timing advance with a realy big street port would be around the 12 deg mark at maximum power, I did not see it in your post but if the engine is equipped with 3mm seals it will not take as much advance as a general rule.

The guy who recommended 25 deg advance is on heroin !

Listen to the other experienced guys who have replied before me, aim towards working towards 10 deg advance then if you want more then slowly step up to it, once you are happy with the power knock off a couple of deg for a saftey margin (to count for hot day if your ecu cannot factor this in or for a bad fuel batch), as one day you will be guaranteed you will need it ! mark my words !!!!