rx72c

iTrader: (8)

ok sorry. maybe i over reacted alittle.

I was always told by many tuners to keep it under 900 degrees celcius and i would be very safe.
One tuner/Seal manufacturer told me to keep it under 750 degrees celcius . lol

I have broken an engine under 900 degrees celcius. It simply pinged very hard and seal bent.

Seal warpage dosnt happen from a short run of heat. A seal will warp under extremely hot conditions over a prolonged period of time.

I could achieve at least 150 degree lower egt temperatures with my car if i had a stronger ignition system. The cranes were struggling to fire all the fuel and water. You have to remember i have maxed 4 1700cc injectors at 75psi of fuel pressure and im using near close to 1.3-1.5 litres of water per minute.

I want to ask you something howard in relation to meth injection/EGT. You have noticed very low egts with your meth injection, were as with me and water injection i notice little to no difference in egts. Have you ever thought(and you may have already posted this) that your drop in egt is from effectively richening your fuel mixture?

I know with straight petrol. Richening fuel mixture has a huge effect on egt and will make it lower. I remember Peter(rice racing) posted that the ww2 tanks run 9.0:1 fuel mixtures and 9 bar of boost and 1:1 water to fuel water injection. Shows you how much water they are using to keep knock down, and how much fuel they are using to keep heat down.

So really in a car. The same should apply and it does. I wasnt able to apply the above to mine due to ignition limits.

I will be able to add more to this when the rx3 is going. It has the same setup as my rx7 but a much stronger ignition. See if i can run richer and see how much lower the EGT's are. But all my other tuning experience shows that effectively rich fuel mixture=low egts.

As it goes now. My rx7 is still going and has survived a very brutal dyno session, alot of abuse on the road and a few highway speed runs. See what time tells.
If the engine does die, it will be interesting to see which apex seals look better as i have half e&j and aviation.

Dudemaaanownsanrx7

iTrader: (23)

One thing about the twin setup howard is/(was?) running is that the EBP was very low. High exhaust restrictions caused by the manifold, turbo, and rest of the exhaust I'm sure plays a big role in EGT's.

I would also think that the water and alcohol would have about the same effects on EGT's. You have to take into acoount the amount of boost you're running compared to howard too. I think he recently turned his up to 20 psi, and you're running around with 14 lbs more. Big difference.

If you're motor would survive without the water, it's quite possible the EGT's would be much much higher without it. Some people with much smaller and lower output systems have shown a 100* F drop in EGT's using water, while others have shown no change in EGT's. Given the amount of heat water absorbs, I would have expected a much more consistent drop in EGT's for everyone.

rx72c

iTrader: (8)

my engine would 100% die without water. And i dont think its from high egts. It would smiply knock itself to death

Howard Coleman

iTrader: (6)

drop in egt... from effectively richening your fuel mixture?

from a recent 506 SAE rwhp run...

psi 20

afr average 11.4
EGT 1647
EMP 26 psi
knock 20
IGL w 12 split... 13, 12.5, 13.5, 14.7, 16.4
duty cycle 69%

850/1600 injectors w 1400 CC/Min of meth

as you can see i wasn't running rich.

howard

Dudemaaanownsanrx7

iTrader: (23)

Oh I know it would. I'm just saying that theoretically if it did run without water the egt's would probably be even higher, and that the water should be doing something in there since it absorbs heat.

rx72c

iTrader: (8)

Howard. Do you think your AFR meter is showing you a true afr reading? running methanol displays completely different afrs so your mixture maybe richer then it the meter is making you believe? This is what i mean.

Dudemaaanownsanrx7

iTrader: (23)

No this is actually a common misconception when taking air/fuel readings from an oxygen sensor.
Sensors read in lambda and output to something familiar to us. Most people are more familiar and comfortable using gasoline AFR's, so that's what the wideband displays.

Lambda of 1.0 is ALWAYS at stoichiometry regardless of fuel type. It just so happens our meters are programmed to display 14.7 at lambda 1.0. So even though alcohol stoich is something like 6:1 compared to gasolines 14.7:1 stoich it makes no difference to the sensor, it will still read it as stoich and display it in gasoline terms, even if you're burning something else.

So if you're most comfortable using gasoline afr's and thats what your meter is programmed to output (many can be changed) then you ALWAYS tune to the same afr's as you would with gasoline, even if you're burning something else.

Howard Coleman

iTrader: (6)

what he said

ronbros3

what ever happened to the old days,, we raced without EGT,, KNock ,, AFR,, and logit, computors,etc.

we may go faster ,but sure can raise the tempers a little, on who is pissin faster.

did Racing Beat drag race an RX3,in 1978 and go 10.60s, and with just a carburator&header?

75% of turbo RX7s cant make an honest 10.60 today,!!

Easy_E1

iTrader: (3)

Interesting thread.

Kansas JoyRide

iTrader: (1)

Oh the profundity of it all.
(For those of you unschooled in the use of the English langue; that mean this crap is truly deep!) LOL

Howard thanks for posting the data earlier; I know there are a lot of hoop to jump through from your setup to mine, but believe or not it helps.

rx72c

iTrader: (8)

In correct.

He gave me AFR. NOT LAMBADA.

SO THE AFR DISPLAYS DIFFERENTLY AND INCORRECTLY.

Look at the data that has been posted. Its afr, not lambada. I can gurantee you. Methanol gives different "AFR" readings.

Dudemaaanownsanrx7

iTrader: (23)

No it doesn't. I'm sorry but you are wrong. Oxygen sensors read the oxygen content left in the exhaust it doesn't know or care what fuel is being used. Since the wideband is programmed to display in gasoline terms then 1.0 lambda IS 14.7:1, it doesn't matter what fuel it is. Lambda NEVER changes and the correlation between lambda and the AFR's NEVER change. (unless you reprogram it to use a different stoich value, which is a dumb thing to do if you're used to tuning with gasoline.)

Here read the sticky posted by Rice Racing, you've mentioned Rice before so if you don't take my word for it maybe you will take his. https://www.rx7club.com/showthread.p...highlight=tune

And another post by Rice taken from the link he posted.

Trots*88TII-AE*

iTrader: (11)

Just to expand on that, stoich for meth is 6.4:1, and the pure meth drag guys usually run a rich mixture around 4:1 AFR for ideal power/safety, for a lambda of 0.625. In terms of gasoline AFR (with the commonly accepted stoich of 14.7:1) it would mean an AFR of around 9.2:1, compared to gasoline's ideal AFR for power/safety of around 12.5:1 (or lambda of 0.85) We rotary guys don't usually play with mixtures that lean though for safety. On 20% methanol, 80% gasoline, the ideal AFR for the mixture would be around 11.8:1 in terms of piston engines, again, we usually play with mixtures alot richer for safety.

Howard Coleman

iTrader: (6)

AFR targets relating to various fuels and combos thereof is always valuable to discuss on our board as lots of people misunderstand LAMDA/AFR.

i stickied a thread on the subject in the AI section for that reason...

https://www.rx7club.com/auxiliary-injection-173/ai-tuning-afr-important-582856/

BTW, RX72C, i re-read your tuning thread in the AI section and want to both congratulate you on your accomplishments and thank you for your helpful disclosure as to your setup.

i am in process of re-doing my turbo system from my twin TO4s that i ran for four years to a single. i am currently designing and building the manifolding. my next project is the adaptation of a Tremec T56 6 speed so i can break 200 mph at the Texas Standing Mile.

given a 550 rwhp V8FD ran 196 and given it's broad torqe range it will take about 600 rw rotary ponies to get it done.

i may, repeat may, try water out as it would allow me to not add a (real) fuel cell for the meth.

i currently run an FJO 156 cell dual 700 CC/Min fuel injector AI setup that works like a charm. i run a Bosch 044 variant pump for the system w a return line after a Weldon adj pressure regulator. it would be a simple task to convert it to water. i have a GZ lower intake manifold that has two additional fuel injector bosses so it would be a simple matter to add some injectors. my elec system is overkill w two Jacobs FC3000 amps and two MSD 8253 coils on the leads. not a problem firing thru water.

howard

Dudemaaanownsanrx7

iTrader: (23)

I reread rx72c's question and actually yes the AFR displayed is incorrect, BUT the richness or leaness doesn't change and therefore tuning using petrol figures won't change, the actual volume of fuel in the combustion chamber does change. If you were running straight meth and tune for stoich, the gauge would display 14.7 but the actual amount of air to fuel in the engine is 6.4:1.

In terms of egt, since your adding a fuel that requires more fuel for the same "richness" then yes there would be increased cooling over straight gasoline, but it would also take twice as much alcohol to have the same cooling effect as water.

Another side comment about running fuels such as methanol is they don't lose as much power when running rich mixtures compared to gasoline. 9:1 for gasoline is quite quite rich. My engine has always liked 11:1 under boost everything just seems happier there.

Trots*88TII-AE*

iTrader: (11)

My comment about the 9:1 was regarding alcohol. If you were to leave your AFR gauge un-touched from petrol and ran straight alcohol, 9:1 would be the ratio you'd be shooting for (0.625 lambda)

Dudemaaanownsanrx7

iTrader: (23)

I was actually referring to RX72c's comment about the old WW2 tanks running 9:1 (w/ gasoline) 1:1 water to fuel, and 9 bar of boost.

rx72c

iTrader: (8)

Your engine likes 11:1 because your ignition cant burn it.

If you had some good cdi's in their you could run mid to low 10s at your power.

As for afr.

I have tuned methanol cars with gasoline numbers, and the afr scale is different. your correct lambada never changes, but when you convert from lambada to afr for gasoline, and your running methanol you are going to get some strange numbers, that is what happen to me, i am only going off what i have found while tuning.

Dudemaaanownsanrx7

iTrader: (23)

I started out with low to mid 10's, It felt fine and wasn't misfiring, but i could feel the power come up when running at 11:1 and knock stayed down so I left it there. I'm sure my ignition could stand to be better, but it's doing the job that I need it to do. I'm not running near as much boost or burning near as much water, so that puts less demands on my ignition system.

I'm not sure I understand what you mean by weird numbers? I'm sure different tuning parameters are required for tuning methanol cars, the burn characteristics, the charge temps and other factors are all different, plus straight meth cars are usually a whole different animal.

But since the relationship between lambda and whatever the gauge reads never changes then the numbers shouldn't be much different when tuning for methanol. 14.7 on the gauge = 1.00 lambda =6.7:1 meth, 12.5:1 display = 0.85 lambda so on and so on, it never changes. Adding methanol will not suddenly make the gauge display 16.5 for lambda 1.

Now maybe you will need to tune for a little richer lambda and therefore lower numbers on the gauge but this is no different then tuning for rotary vs piston, or NA vs boosted, or 5 psi vs 20 psi. That's what tuning is about, finding what richness (or leanness) the engine works best at for the job at hand.

Dudemaaanownsanrx7

iTrader: (23)

I found 2 charts that display AFR for Methanol vs lambda and gasoline vs lambda, I've combined them into one chart. The methanol side didn't have as much information so I filled in what I had, interpolation can be done to figure out most of the missing cells. If one wants to tune for a certain meth AFR, while using defualt wideband programming*, just find the AFR you desire and look across for lambda and the correct Petrol AFR. *(Default programming uses gasoline AFR's)

rx72c

iTrader: (8)

I think your missing what i am trying to say.

To get an engine to run on methanol. As someone has said before, It needs much richer mixture to run (in gasoline terms). So what i am saying, by adding methanol(and im not talking about AI, im talking about methanol injection), what happens to the mixtures? how do you interpret the numbers? It could be richer, it could be leaner, this is something for howard to answer, not me. But when you add methanol into the equation, does the mixture get richer? So without methanol if you had a 11.0 mixture, and then put in methanol, does the afr meter pick a difference?

As for your car feeling more powerful at 11.0, its your ignition. It dosnt have to miss to be missing out on power.
If your car is reliable with the current tune up, then you have no problem. Everyone has their own way of achieving similar things. Their is no wrong or right when it comes to tuning. we all base our current tuning based on previous experiences etc.

Howard Coleman

iTrader: (6)

just a couple of observations...

just so we all are clear:

when i add meth i subtract base fuel (gasoline). that's why i am at a low duty cycle.

as far as straight meth just as an FYI.

i have a friend who shall go nameless that runs a 100% meth 2 rotor. he has been making over 1000 rwhp for a few years. he runs 14 1600 injectors at 76% duty cycle at .69 Lamda.

that'd be about 4.45 AFR Meth and 10.23 Gas.

no intercooler. you wouldn't want to put your hand on his upper intake manifold after a run. you might not be able to remove it. think ice.

howard

Dudemaaanownsanrx7

iTrader: (23)

I'll admit I have no direct experience with methanol, but from what I've read it runs fine with "normal" mixtures. Lambda 1 is Stoichiometric or "optimal burn" for all fuels, and numbers above and below that would still be a lean or rich % of stoich. The comparison of an all out drag car running 4:1 Air/meth ratio (.625 Lambda) with boost levels over 50 psi isn't really comparing apples to apples. Of course it needs more fuel! Those rich mixtures are required to keep knock down at those extreme levels of performance. The further you push an engine the more and more fuel of any kind you will need to keep knock at bay.

Howard is running 30% methanol at 20 psi and 0.775 lambda. Thats a considerable amount of methanol with leaner mixtures then could be done with straight gasoline. In one of his writeups he mentioned the map sensor not be connected and the car leaned out somewhere in the 13's, still no knock and picked up 30hp. Rice has mentioned running in the 13's with water injection injection also. So personally, I believe a normal performance car running methanol will hold up better at leaner mixtures then a car on straight gasoline. Same for a water injected car. But the advantage here with meth is you don't lose the same kind of power running rich as you would with gasoline. So you can have that added safety net without the same sacrifice.

Another thing about methanol is it needs much more timing due to the slower burn characteristics.

Also fuels do make different power levels at varying AFR's. You can have an ignition lighting everything just fine and pick up power by leaning it out. Even you're engine (rx72c) would make more power at 11.5 compared to 10.5, but it wouldn't be as safe. This can be seen simply by changing the fueling at idle, if it's too rich or too lean, idle speed lowers indicating less power in the combustion.

(EDIT: Howard looks like we tie for timing on our posts at 3:05, you were a few seconds faster though...must have been the meth)

rx72c

iTrader: (8)

did i miss something?