Weird thing while tuningg my S-AFC...
If I lean it out a get much more power!

-10 or so through the midrange gives a very noticable kick over the stock settings.

And whats the deal- I have a ported engine, with full intake and exhaust..
I should be able to add fuel at high RPMS to get more power... but NO!!
Even 1% more than stock gives a little less power- I get more power my dropping it down by -4% or so!! It sound's little higher pitched too..
Weird... I have a stock fuel system.... I am at a loss. This mean that with the extent of mods I have, I am still nowhere NEAR the limit for the stock pump and 460's???? I'm now running a 14sec 1/4 at 100mph!! The numbers don't add up.
I know that with 2cycles, once an engine is broken in, they lean it out a bit and get more power, but it burns hotter... well, I havn't heard or felt any detonation, but I havn't dropped below .9 on my stock o2 sensor..... Strange.
Anyone have any input?

 

I tried telling people that 4x550 was too big for an NA, but NOOOOOO. don't listen to me...

 

i always thought more fuel with those mods would yield more power too? wtf? i have always been recommened to chip up and upgrade to a s-afc and **** after all the bolts etc. hm.........

 

You need to read up a little on how combustion works. More fuel does not equal more power. More air with the correct amount of extra fuel makes more power. Generally too much fuel hurts power. The leaner you go the more power you make but the higher the combustion temps and likelyhood of detonation. You should always run a little rich at the top end for safety's sake. Consider getting it tuned on a dyno; it shouldn't take more than an hour (probably a lot less) to get your S-AFC tuned properly.

 

damn your running 14s!!! at 100mpH!!!!!!!!!!!!! and your using less fuel.............hrmm dunno,
btw who street ported your motor?
I would think that you would use more fuel if it was street ported..
dunno but with all my mods the best I could do at the track was a
16.3 at 84 MPH, and I think I should be doing better than that, and wanna stay N/A and get in the 14s where you are..

 

i was thinkin that if u opened up everything and teak every bit of hp outa of it u would be taken more air in. U know kinda like a TII that opens its **** up, allows more boost i know, but still. I figured it would be running lean with those mods, plus a ported..

 

Fuel is need based on how much air your engine is sucking, hence A/F ratio. And yes it is true that leaning the mixture will produce more power (and stoic will be most efficient at 14.7:1 so that's why during normal cruising, you ECU searchs for the best a/f ratio at around .5V from the O2 sensor). But, decreasing the mixture also builds heat during compression and can lead to detonation. If you are getting more power from your action (I don't know how that could be since your fuel system is still stock) and are still in the "safe" a/f region, then that's the way to do tune for power. Also, the O2 sensor can be inaccurate (it gives you relative reading errors instead of absolute error readings) and only an expensive wideband sensor can tell your readings for sure.

Jay

 

I I am getting the wideband o2 from Techedge- but My o2 sensor voltage at full thottle is around .90-.94 or so.
It is odd.
It would make a tad more sense if this was the case on a fully stock engine, but it is very strange on an engine that has been opened up a lot.
Well, Bottom line- leaner mixtures burn hotter, and when tuned at a precise point, yeild the most power- So what about all the guys telling me that these things run best at 12:1!!!! (That's supposedly N/A too)
If I ran my car at 12:1 it would be hesitating like crazy.
I guess first hand experince is the only way to tell.

 

12:1 is on the rich side of stoichiometric, but it's far from excessively rich. On the contrary it's quite normal, and will give you lots of smooth safe power. No offense, but like I said, you should do a little reading about this stuff before you start trying to tune cars. I've also said before that stock oxy sensors and aftermarket A/F gauges (which are just pretty voltmeters) should not be used for tuning. If you don't believe me, read this:

The Technology of Oxygen Sensors

 

Bah' that's what you think

BTW - Thanks for the advice, about 4years ago

 

I thought it was pretty known that NA chips like the MD race ones leaned out the midrange and aggressively advanced timing at lower rpms backing off at higher rpms. These chips usually suggest higher octane fuel I believe, whereas the best power on stock set-up is w/ lowest octane. I wasn't surprised to hear porting didn't require more fuel in midrange- doesn't porting help high rpm VE?

 

well,i dont know to much about tunning,all i can say,is,from a conversation with the guys at mariah motorsport,they told me that they run theyr race prepped n/a's pretty lean,and told me that a n/a rotory does not mind beeing on the lean side a bit,and it will make best power there.but,of course,for the novice[w/o the budget to overhaul your motor every month or so],that might be rather unwise....i'm sure most every one here will tell you the same.the thing i was wondering,is,i assume you leaned the mixture out at idle,right?did this help with that nasty sulfur smell,that a[especially non-emission]rotary seems so adept at producing??i was under the understanding that what your smelling is mostly due to a rich mixture.would love to know
~david

 

Bambam7: I know what exactly what you are seeing, I saw the same thing on my TII, I started off with the s-afc jacked right up and did some G-tech runs, the leaner it got, the faster it got.
I think sometimes more fuel is just used as a crutch for not haveing good enough fuel, or to much timing when it comes to TII's, anyway..
I got mine down to the point where I was in negative correction in some places and only adding extra correction at idle, and at 6000 rpm plus, the car was the fastest I had ever seen it. I am not really sure about the quality of gasoline though from different stations, so I went back to the plus correction as a safety margin, If I could guarantee some how the fuel I was getting was always 92 octane, I would run back in the leaner side of things, but I lost a 440 to pretend premium fuel once, and a 13b is twice as much to build as 440, so I play it safe and run richer, but with a slower car...Max

 

Bambam7,
This is just my opinion...but 12:1 is too rich for an n/a. I would target 13:1 instead. The only reason people are running that rich on a n/a is to be safe, but I think this is too excessive. I can tell you that I target 12.5:1 max WOT on my TII. I have been running this setup for 1.5 years now w/out problems, or blown seals. Jay

 

as strange as it may seem, unlike a piston engine a rotary motor makes peak torque with the a/f at 12.7:1. and peak torque means peak HP for that RPM. tune for 12.7 thru out the rev range for maximum power thru out the range, to make it easier on the wallet 14:1 in the cruising ranges is fine

 

The FC's normally are programmed (stock ECU) to run a bit rich in the midrange.&nbsp We've had good results with dropping about 3%-5% in the midrange around 3kRPM - 4.5kRPM.



-Ted

 

For turbos' right? Unless someone can prove me wrong with FACTS, any engine will make the mnost power at just richer than stoich, say 14.0-14.2:1

But, turbos should be tuned for about 12:1 under boost to prevent detonation. 14.0 will make more power, but the chance of blowing your engine is very very high once the boost levels go up. Ignition timing also plays a major part. A n/a might make more power at 13:1 with the timing advanced to take advantage of the richer mixture than one with stock timing at 14.0 mixture.

 

Well, I'm getting a wideband o2 sensor soon, and I am also getting my S-AFC tuned on a dyno.
Then I'll be able to tell everyone what mixture yeilds the most power!- Enough speculation.

 

Are you running any ignition advance?

If not, then detonation should not be your main concern. EGT's are very important. Leaning out your engine causes it to run hot, in some cases real hot. I know that in combustion engines, you dont want your EGT's to get much over 1350 deg. F for sustained period of time, because it will overheat the block, being aluminum and having a melting temp less than 1100 deg. You can get away with the higher exhaust temps, because the hot gas does not stay in one spot, and has very little time to transfer heat to the head. Especially since the exhaust port will only see hot exhaust gas every other stroke. In a rotary, the exhaust output is sinusoidal, and comes 3 times a revolution. So, the hot gases have more time to transfer more heat to exhaust surfaces. Hence, our engines run hotter.

Now, I know some guys that will tune their rotaries to run very lean for very short periods of time at EGT's of up to 1650 deg. F. And they make a lot of power. But I dont think that any of them would recommend that you run those sort of EGT's every day on the street.

Mind you, I dont do this to my car and would not recommend that anyone do it to theirs.

 

Depending on EGT sensor location...

I've seen EGT's as high as 880C, which is way over 1700F.&nbsp EGT probe located in the stock turbo exhaust manifold.&nbsp In the Racing Beat 3" downpipe, it'll show around 850C.




-Ted

 

Dont think so, on the haltech help list a while back Matt (the HITman) who has tuned more rotary's than you could ever imagine, said 12.7 was the a/f ratio that a rotary makes peak torque/power at

another tuner i know said:

10.5 to 10.9 : 1 = rich (results in about 10% extra wear due to over fuel)

11.0 to 11.5 : 1 = ideal (for engine life)

11.6 to 12.5 :1 = ideal for max power (HIGH risk of engine failure "detonation" at power levels over 380rwhp)

 

Those numbers arent for turbo's though??
I don't see to many N/A's with 380 rwhp.
I have gotten a lot of people telling me things who don't seem to realize a very large difference in fuel demands between a turbo and N/A setup.
If those are numbers for N/A, I've been looking around for months and gotten a LOT of different answers. Granted, every car is different, but it's nice to know what I'm looking at now.
I'm probably going to aim for around 12.5:1.
I don't have an EGT, and I don't plan on geting one- The wideband should be enough- I don't plan on cutting it so close with the mixture that I would worry over-leaning and over heating.
I can't wait to get the wideband installed!

 

Rob at Pineapple likes to see 1850* under full throttle in top of 3rd or 4th gear. CJ

 

Stop posting numbers for turbo cars!!!! His car is not a turbo, and needs to be much leaner than any turbo motor.

N/a's like a lean mixture compared to turbos. It goes that way for any engine, but especially rotaries.

 

Here is the deal. Stoich is 14.7:1 we all agree on this, but this number is only good for part throttle cruise, not WOT under full load.

WOT on a NA motor you want 12.5:1 to 13:1. Leaner is meaner. Forced induction 12:1 to 12.5:1. These numbers are on a piston motor, if somebody knows they need to be richer for a rotory post some numbers, I do not see why it would be that much different. It's still an air pump, just as a piston motor is, but I have seen somone post they need to be richer. But how do you know if they know what they are talking about.

Getting the wide band a/f meter will be the best tuning tool you will ever buy. On my 87 TII which is completely stock I saw 10.5 to 11:1. Definately more power to be had. But Mazda is more concerned with warranty issues so they run them fat.

Remember leaner is meaner, so it might feel like great but may hurt your motor, so get that wide band a/f meter.