Kansas JoyRide

iTrader: (1)

Ok, I know this may bring out the flamethrowers, but after several searches I can not find what I am hoping for so here goes nothin. First, I try not to ask a question on this forum unless I have done my best to do my own homework and second I do my best to set up my questions so that anyone who cares to answer has the info they need to give a good answer. Here is my question; is there is a link to a chart or some sort of data that would give me a better set of parameters for EGT numbers under varying conditions such as idle, cruise, boost and so on?

Here is my set up. 93 with new rebuild with large street port, Aspec 500r -coated, 550 primaries, 1680 secondarys. Excessive UIM, Twin-Power, RB catback, magnaflow, and the down pipe and header are wrapped. I have the Pineapple dual EGT gauge installed with the probes located immediately off the rotors before the turbo. No air pump. I am very slowly working on my own tune and would like to have a better idea of generally acceptable EGT's. If anyone can give me a link or share some info it would be greatly appreciated. THANKS

Gringo Grande

iTrader: (97)

Probably might not be 100% what you are looking for but this is in the Single Turbo section and if you have a Power FC may help: https://www.rx7club.com/single-turbo-rx-7s-23/single-turbo-pfc-tuning-document-here-374526/page4/

http://www.catenet.net/rx7_tuning.pdf is the link for the tuning info.
http://catenet.net/dyno.php

arghx

iTrader: (3)

The reading you get does depend on the location of probes and how responsive your gauge is. I'm not sure how responsive the Pineapple gauge is. My old autometer was very slow.

I think you will read a few numbers here and there about 'ideal' EGT's... mostly in the 1550-1600 range preturbo. On straight pump gas those numbers will be frequently exceeded, especially during hard driving. I took my car to VIR a couple years ago and I remember my EGT gauge pegging at 1600 after the turbo for most of the run.

Right now I am running a loggable EGT on my Datalogit. I can tell you right now that my EGT's sometimes are in excess of 1800 peak preturbo, at least on the rear. The last decent reading I got was 1650 on the rear rotor and about 1550 on the front, but then I fried both probes. I have since turned up the boost two more pounds (16psi) and have been taking it up to 8000 rpm. I've got 8.5:1 compression rotors running 93 octane gas.

The short answer to your question is: there's no hard and fast answer as to the limits of what's 'safe'.

Trots*88TII-AE*

iTrader: (11)

Just to add to the above, RX72c ran up to 34psi on pump gas and water injection, and had pre-turbo EGT's at about 1050C, which is nearly 2000F. Alot of people will tell you if you ever got near there your motor would be toast, but he's running strong at over 700whp. What works for one will not work for all.

Zero R

iTrader: (1)

^ Or what works for one for awhile, may not be what works at all over time. I'm sure the OP has a completely different set of goals than RX72c does.

classicauto

iTrader: (3)

Porting will also play a big role with regards to EGT's, and what is safe.

A high overlap setup with above "average" egts will be ingesting more of that heated air then something with a less aggressive port.

There's no real answer though. The key is to keep them as low as the setup and tune can manage and then thats all you can do aside from adding other components like AI or larger exhaust to reduce it.

Howard Coleman

iTrader: (6)

you have a nice setup. since your turbo can make over 70 pounds of air per minute you can easily be on the sunny side of 500 rwhp. anything materially over 400 and you need AI or, at a minumum, you will warp your steel apex seals and lose compression.

if you are running steel seals you don't want to see anything over 1800 and, as a number of posters suggest, 1550-1650 is a nice range. BTW, don't forget to use egts to tune the zero to 14 psi boost range. you don't want to be looking at 1100 in this area. work w the timing and afrs to get it to 1400.

hc

Kansas JoyRide

iTrader: (1)

This is very helpful information, thanks to everyone for taking the time to reply.

Howard I don't know if you recognized my login name but I am the guy who purchased your old set of wheels. Unfortunately my engine went about the same time I got the wheels and the car has had very few miles since then. I decided I better learn every aspect of my car if I was going to keep it, as there is no one very close to me who works on these. I pulled my blown motor, installed a rebuilt short block built by Glen from Arizona Rotary Rockets, (Glen is a great guy and has been very very helpful), installed an aftermarket water pump, my turbo setup, Greddy front mount, new wiring harness and on and on. It has been a very long and very slow process going from a basically stock car. I have plagiarized a lot of my setup from your posts including my fuel injector controller and your "remove the useless oil level send and install an oil temp sending unit" idea.

Thanks for your tip on keeping the egts’ in the correct range through boost. I might easily have done that wrong. I stopped my tune to chase an issue I noted on my egts and to solve an oil leak (not sure yet but I found 3 of the studs used to secure the oil pan reinforcement plate to the pan that were just hanging on. I broke them off with my fingers) It my also be leaking oil from the motor mount bolts.

Anyway my idle egts are running rich in the 12 to 12.5 range so I took some fuel out. I immediately noticed that my front egts jumped to the 1350 range but the needle for my back rotor had not moved. My egts were still about the same. I had notice even before taking out the fuel at idle that I was running a spread of about 400 degrees between the front and back rotor through out the range of rpm and boost up to about 5 psi (as far as I had gone on my tune) consistently. I am guessing that I may have one of my 550s dripping on me which would explain the high egts on one rotor and no movement of the needle on the other. I purchased the 550s used from a member who stated they had been freshly cleaned and flow tested. He sent the paper work with them so I am not sure what to think. I read somewhere that Mazda had some early problems with the 550 due to excessive fuel pressure causing them to drip. I am going to turn down my fuel pressure and retest the egts at idle to see if that makes any difference.

As far as alternate injection goes, I am a fan. I was running one of the early CoolingMist two stage setups on my car with the first engine. I hope to be able to add tunable AI in the near future.

Again, thanks for all the replies, you guys are great. I have the answers I was looking for

jetlude

iTrader: (9)

Are Atkins apex seals made of steel

arghx

iTrader: (3)

400 degrees between the two rotors? Are you sure you have good placement of the probes?

Kansas JoyRide

iTrader: (1)

Yes, the probes are mounted using stainless steel bungs braised to the headers at identical distances off the exhaust ports. My first guess is an injector dripping. I will however go through every protocol I can think of, compression, coil pack, timing and anything else that comes to mind. Seeing one rotor with elevated EGT and the other not even registering at idle after taking out fuel and still seeing AFRs in the 12 to 12.5 range is a good indicator that one rotor is pig rich. I also notice that after transition, above 4k RPM, the variance between rotors shrinks to around 100 degrees. I hope I get some time to work on it soon. I miss driving my 7. Thanks for the post. RD

Howard Coleman

iTrader: (6)

you are supplying helpful observations.

typically rotary EGTs can differ front to rear by 100 F. you have the Excessive LIM which should allow you to tune to equal EGTs.

since your EGTs converge above transition it certainly could be an injector. 1350 is amazingly hot at idle. what do the plugs look like? i would let it idle for a while and pull the lower plugs for a look.

the Excessive LIM has two injector ports that generally get blocked off. if one of those ports was leaking any air you could get too lean at idle but with the higher air volume at transition it could work o k. check the two additional ports for leaks.

the Power FC does not allow tuning fuel at idle below a particular delivery rate. if you are at 1300 EGT on one rotor at idle you are getting air or possibly, not as probable, your timing is way off on one rotor.

BTW, if you don't have a datalogit get one and switch your EGTs to digital. you really need to read your data in the 400 cell digital configuration. as well as fuel pressure and AFRs.

i am happy you are taking good care of my wheels

howard

Kansas JoyRide

iTrader: (1)

That's a interesting thought. I will check to see if I am pulling any vacuum on the front injector port block off plug. That would make sense. Good call.

Yes I do have a datalogit, I will have to study up on wiring egt and fuel pressure to the datalogit. I already installed an electronic fuel pressure in-cab gauge. I am sure there are lots of "how tos" for connect stuff to the datalogit on this site.

I have a question on the location of the fuel pressure gauge sending sensor. I wasn't thinking about an opportunity to do actual logging of fuel pressure when I plumbed in the sending sensor for my fuel gauge so I wasn't real picky about where I located it. What is the right location for this; i.e. prior to the regulator, on the return fuel line (where I have it now) or somewhere else?

The RX7 may be the prefect project car, kinda like surfing the web, you can never really get to the end (of thing to work on), not that I would want to.

Dudemaaanownsanrx7

iTrader: (23)

Actually even people with equal flowing manifolds have been reporting different temps front to rear in egt's. My speculation is that the rear rotor just runs hotter from being in the rear and having hotter coolant flowing into it and overall just retains more heat. But most people only see a 100-150* difference between rotors so definitely something isn't right if there is a 400* difference.

Something else I would suggest is switching the front and rear probes if that's not too difficult. This would tell you if there is discrepancies between the probes rather then actual readings being off. If the temp differences switch rotors, then you know something is up with the probes.

Kansas JoyRide

iTrader: (1)

No they are very easily accessible. That is a good idea. I will give it a shot. Thanks

Monkman33

iTrader: (28)

How aold are your injectors? I just decided to purchase new primaries instead of dealing with the problems that could come with older/serviced injectors.

Also, I am very pleasantly surprised by your demeanor on this forum. Your posts are thorough, and easy to read. You listen to suggestions from the smart ones on here, and you have a general maturity about your posts. I wish you well in hunting down your gremlins.

Also, check your plug wires and coils along with your plugs. If one is messed up and arcing, or not connected... you could just be flat out not igniting fully on one rotors too.

arghx

iTrader: (3)

remember that even on piston engines there can be variations between cylinders. Modern Subarus have cylinder specific adjustment maps in their factory ECUs.

rx72c

iTrader: (8)

Variations at idle and cruise are not to be concerned about unless the gap is 70-80 degrees celcius+. That means you have either a injector flow issue or a compression issue.

On boost is different. Ive found on boost and at over 3-4000rpm compression has little effect on gap in EGTs between rotors. My last engine which got damaged in one rotor pretty badly, had 300 degree different to the other rotor in egts on cruise and idle but on boost was with in 10 degrees of the other rotor. Car still made 500+rwhp as well.

as for safe egts. Their is no safe EGT. I have run higher then 1050 DEGREES CELCIUS and my engine has not failed. People should open their eyes to KNOCK. This is what kills engines. Keep your knock to a minimum, your car will hold together. Mine is currently doing so fine.
It took me a few engines before i realised i was looking for problems in the wrong place.

It is all about Knock.
Lean fuel mixtures create knock. Excessive timing creates KNOCK. Rich missfires create knock.

So when your trying to eliminate knock, look at what you need to do eliminate knock.
Water injection. Rich fuel mixture, Conservative timing.

Then you need to make sure your car can do it again, and again and again, and is not inconsistant. So tip top fuel system, OVERKILL OVERKILL. A tune that has a huge safety buffer. A STRONG IGNITION THAT CAN BURN THROUGH YOUR EXCESSIVELY RICH FUEL MIXTURE.

You will get alot of guys crap on here and send you the wrong way. Above is very important.
I cant stress it enough.

Kansas JoyRide

iTrader: (1)

Primaries where purchased from a member on this forum. They were advertised to be freshly cleaned and flow tested, the receipt and paperwork where in the packing with a current date. Doesn’t mean I should eliminate them as the culprit though.

Thanks for the kind words, I figure if I am asking people for help with a problem the least I can do is be respectful and appreciative. It is up to me to sort the sense from the non-sense. Besides, at my age I had better be mature.

Makes sense that a solid ignition system would be very important to these engines because of the damage that knock can do to the hardware. Thanks for your comments.

I really appreciate this input. I had already decided I did not know enough about how knock is measured with these engines. For example, my first rebuild was done by the RX7 store almost six years ago. The knock sensor reading fresh from the shop read almost 40% of the bar graph on my PFC handheld. Under acceleration it would jump up to 3/4 or so. Seemed high to me, but I trusted the guys at the shop to know better then me. I just didn't have a good benchmark. When that motor went about 3K miles later I broke it done and found my front rotor caved in and both rotors with dings on every face.

Glen at Arizona Rotary Rockets built my current short block. At idle, using the same handheld but with a different sensor, the bar does not even register. At first I though the sensor was not working but under acceleration to around 5 psi, the gauge will bounce up to maybe 20% on the bar.

I have read that the reading at rest can vary without meaning much. The way I understood the posts I've read is that the reading at rest is more like the benchmark for your sensor; it is the amount of movement from that point that matters. I don't know enough about this to know if this is good information?

Just applying logic to it, if the sensors are not calibrated to show no noise under no knock situation and are simple picking up normal engine noise then I guess that could create a high reading at rest that would have no connection to knock. On the other hand, if that is a faulty assumption, it could simply mean you have a significant problem that escalates under load or acceleration. I know I need to understand these issues better.

To be clear, I understand what knock is and what to do to work toward eliminating it when it occurs. What I don't know enough about is how to measure knock on a rotary engine. Anyone willing to provide information is welcome to jump in. Thanks for taking the time to submit your replies; this information is some of the more helpful I have received over the years. Sorry for the long post!

Dudemaaanownsanrx7

iTrader: (23)

I have never seen or heard of rich misfires causing knock. Not to say a strong ignition isn't important for a properly running engine, just saying Knock is caused by irregular combustion, generally from ignition before the spark plug fires. Misfire means the combustion wasn't ignited when the plug fired, and aside from a performance and emissions standpoint I don't see how physical harm could actually occur.

Some more modern knock sensors are designed to listen for combustion as well as knock, if combustion doesn't occur it's reaction is the same as it if it is hearing knock, so it pulls timing and probably flashes a code or other warning information. The rx7 knock sensor is just a microphone that listens for a certain frequency range, so It doesn't actually listen for combustion to occur.

Howard Coleman

iTrader: (6)

"I have run higher then 1050 DEGREES CELCIUS and my engine has not failed."

it's really great that you didn't blow your motor while running "over" 1922 F. so what. most apex seals are steel and they all warp at these temps. in addition, rotor housings which are up 93% in price since july 07, greatly suffer.

to directly answer the OP's question... "you don't want to see anything over 1800 and, as a number of posters suggest, 1550-1650 is a nice range."

often the EGT benefit will come from finding your readings are too low between zero and one bar. this often happens when your AFRs look perfect. change the timing and look for 1400 F in this area.

absolutely knock (agree w rx72c) is one of the 3 indespensible tuning tools along w AFR and EGT. and they all need to be logged on the 400 cell Datalogit grid.

FWIW, i greatly respect the stock FD knock sensor. chasing a weird knock reading i swapped in 3 different sensors and they all read the same. further, if carefully watched, knock readings will point you toward tuning limits.

the problem w the rotary is that due to the somewhat fragile nature of apex seals you want to tune short of knock since knock can result in immediate damage. EGTs can greatly help as they provide an early warning sign.

how important are reasonable EGTs? consider gasoline, all gasoline, auto-ignites at 480 F! if you are running high EGTs and sweep some of it back into the next power impulse you better have water or alcohol cooling things. water doesn't auto-ignite and alcohol auto-ignites at 850F.

autoignite =s knock=s a call to Glen.

howard

rx72c

iTrader: (8)

in reply to the above. do you really think your apex seal or rotor absorbs all of the heat produced by your engine? if this was the case then your engine would fail on idle.

My engine has seen over 1050 degrees celcius. Id be happy to take a camera in my car next time and show you live readings of my egt's while getting up it.

So your theory of melting or plastic deformation point of metals goes down the toilet. I will say it again. Engines end up the way they do from KNOCK. Im not going to beat my head against a brick wall, if you want to listen, go ahead, dont want to, thats up to you. Youll learn the hard way.

Howard Coleman

iTrader: (6)

of course apex seals don't absorb "all" the heat and if you actually read my post you will not find that stated. apex seals do receive heat from combustion and raising combustion heat raises apex seal temperature as well as taking the starch out of the apex seal springs.

given your significant experience w rotaries i would expect you have seen more than a few warped apex seals. Peter has a rogue's gallery of pictures of the typical rotary apex seal pullouts.

apex seals most often warp from excessive heat. generally, they break from knock.

keeping EGTs in the proper range helps avoid knock. EGTs function as early warning.

i do not disagree w you re knock.

as to warped steel seals, my guess is that any rotary running more than one bar without some sort of AI has somewhat warped seals from making 460+ flywheel hp from a 159 cu inch engine... almost 3 hp/cu inch. most rotary guys don't realise what a high state of tune a "moderate" 400 rw hp is in...

i also do not dispute that you ran the EGT that you did. i just want to suggest we mere mortals don't go there.

Kansas JoyRide

iTrader: (1)

For purely selfish reasons, I would hope this thread would not turn into a debate between well-intended people. I really appreciate all of your responses and, so far, I have not seen a single post on this thread that I considered to be of no value. For guys like me that is the bigger point. I would find it much more helpful to hear about how to interpret the readings coming from the knock sensor. Rx72c, can you help me with that? You mentioned a video of your EGTs, that would be a lot of trouble but, based on the point you are making, it would be much more helpful to me to hear about what your knock sensor reading are showing and how you interpreter them. Do you recommend tuning for a completely quite gauge (if such a thing is possible)? If not that would mean somewhere between zero and off the scale there are reading that are actionable. Are all indicators of knock something to be acted on or is there a “normal” amount that is of no concern? Too all who are replying hear, I would suggest that this is the kind of information that would make this a much more valuable post for anyone who reads it. Thanks

Dudemaaanownsanrx7

iTrader: (23)

There's a lot of information on the forums about safe knock levels. But most tuners decide for themselves what is safe. I personally try to get them as low as possible. My current tune at 23 psi has low 20's, and i use the pfc to monitor knock. I would be concerned if i saw much over 40. You also have to determine if what you're seeing is knock or other noises from loose parts or drivetrain slack. Knock readings under boost is what's important. High knock readings under cruise is generally other noises. Some knock sensors just report more noise in general, so you have to kind of get a baseline and go from there. My knock sensor stops working from time to time and just reports 1, but i feel confident in my tune not to worry about it. Thats where conservative timing and ai comes in, that way even when you cant monitor knock,. or you get a bad tank of gas or whatever you can still expect the motor is safe.