23Racer

I ran the car this past weekend at Mosport and all the old issues raised their heads and its driving me nuts. Fundimentally I have to be missing something. The last time we tested the car was at Shannonville and it went like stink. The track is a 2.5 mile with lots of corners and a few longish straights (longest about a 1/4 mile). Fastest straight line speed is about 110 mph. Ambient air was about 90 degrees with lots of humidity. The car ran like a monster with no issues.

So this past weekend we raced the car at Mosport again. Mosport is another 2.5 mile track, but one of the fastest in North America. Average lap speeds are in the 90's and the car needs to pull hard to 8,000 in 4th (4:10 rear). Morning race, car ran great for about 2 laps, then small detonation on long pull up back straight. As the race went on, the detonation got worse until I could only pull for short bursts, then lift to just over an idle speed accel. It would pull hard in 2nd without issues, only hard pulls in 3rd and 4th would cause light detonation. Ambient air was in the low 60's. We brought the car in checked the logging and the car was running A/F's in the 11.5 to 12.5 range and we had pulled the timing back before the race so that it was 22 degrees total below 4,000, 18 to 6,500 and above 6,500 at 16.

We fixed an intake leak before the second race in the afternoon and thought we had it nailed. The only differences were that ambient air went up to mid-60's and that we had fixed the air leak. The car started detonating as I nailed it coming to get the green flag. Water temps had climbed to 210, so I started to short shift, but the detonation was far worse than the morning session. I really just coasted around the track and brought water down to 180 degrees, but as soon as I tipped into the throttle and put the car under load in 3rd or 4th it would detonate.

Ideas? Clues? I am going nuts as the car worked so much better at Shannonville that we thought it was licked. Is the timing to far advanced for longer high load pulls, Why does the detonation get worse depending on throttle opening, versus speed or load effects, especially when air, fuels look fine. Plugs are sooty, exhaust is sooty, so we don't think its a fueling issue. It seems to not be water temp related, but a few degrees in ambient air at Mosport effects it, but not at Shannonville wher it was 30 degrees warmer. Why only at Mosport with higher speeds and loading for longer?

Any ideas or help would be appreciated. I am getting very frustrated as the car works so well at the shorter tracks and you can beat on it like a bull. Its like fine china at Mosport and just won't work.

Eric

23Racer

Doing some reading up on splits. We are running a constant 5 degrees split. Could this be contributing to it? When I put the (11.5) race plugs into the motor, they corrected for ignition concerns and transformed the power bands, but they did not help.

Could it be something fundimental like using the S4 eccentric shaft pulley to set TDC and using S5 NA rotors and S4 TII housings? This mishmash of parts makes us think we are running this timing, but in reality we are far further advanced?

I am grasping at straws as this has gone on for 4 years now with tremendously variable results at different times of the day.

We were also running Shell Premium Fuel as a base fuel at both tracks.

Eric

Liborek

From the pictures of your setup, ITBs are breathing underhood air? I´m not sure but certainly something to consider. Does knock occur everywhere or around torque peak?

23Racer

After the car runs for about 3 laps, everywhere where there is load and the larger the throttle opening, the more knock I experience. I did consider under air temps, but when the car ran at Shannonville the underhood temps were in the 45 C range with no issues at all. At Mosport we were seeing underhoods in the high 20's. I run a 4" duct from the nose to the trumpets and have a motor to inner fender steel heatsheild in place below the trumpets.

It is more of a long pull issue, that seems to be unrelated to water temps, Air Fuel ratios, oil temps and rpm. Just throttle opening and load and the timing is at 16 degrees advanced when it is happening. Maybe I should just pull a ton of timing out of the car (10 degrees so it is at 6 degrees above 4500 rpm) and start over. Freakin annoying as it didn't do this with the stock S4 ecu and the Holley.

Eric

Shainiac

iTrader: (7)

Why'd you change the timing if it was running so well before? Maybe try your old timing? There are a lot of variables since the last race, it seems

23Racer

Other than the track difference, the only change we made since Shannonville, was to pull a bit of timing out of the motor to give us a margin for error. I just found this which is confirming what I am leaning towards,

The RX-8 uses a very advanced engine management system. Besides precisely controlling the operating parameters of the engine, self-preservation (of both the engine and the catalytic converter) is also considered.

The engine management system continuously monitors all engine functions and adjusts accordingly. For example:

Under heavy load acceleration, the timing is retarded and the fuel mixture richened to reduce the likelihood of pre-ignition or spark knock. If spark knock is encountered, a knock sensor senses the condition and further retards the timing. Gradually timing is advanced and fuel mixture leaned after the load is reduced.

A second reason for fuel enrichment is that when timing is retarded, exhaust temperatures increase; a richer mixture lowers the exhaust temperatures and reduces the chances of damaging the catalytic converter.

What do you guys think? I wonder if I am getting so much cylinder filling with the ITB's that at Mosport it is working under a completely different load pattern and it starts to detonate and gets hotter and hotter until it is very poor. At Shannonville, I would be under full throttle/ full load for at most 7 seconds and total 45 seconds with lots of overrun time for chamber cooling. At Mosport 65 seconds a lap and the longest straight time is about 30 - 35 seconds.

Eric

Liborek

This is true. Mixture of about 0.7 Lambda gives highest knock protection.
Unfortunatelly, this method cannot extinguish knock in rotary engine. At least not in Renesis.

This certainly puts very high load on engine, especially in high gears, but on the other hand, this high speed stuff should be easy to cool in terms of water and oil. You should look for problem elsewhere. Your ignition timing doesn´t look overadvanced, but without actual test, its just guessing, as you have unique combination. Any chance of ignition crossfire? Possibility of trailing firing first? Best would be oscilloscope and measuring

arghx

iTrader: (3)

I haven't kept up with all the details of your car. Can you give some background? What is your setup? What fuel are you running? How do you know it's knocking?

23Racer

Okay, time to bare my britches as I am at a bit of a loss. The keg is an S5 NA rotating assembly with stock Mazda seals, etc.... in an S4 TII housings and end plates. It is a 1/2 bridge setup with a Racing Beat Road Race Exhaust Port, Judge Ito Monster Street Port Primary and Racing Beat Racing Bridge Port Secondary Port.

I run a Racing Beat Road Race Header into a double 2" exhaust through a merge collector at the diff into a single 3" exhaust. The ITB Setup is 4 50 mm Hayabusa's through a 9" manifold, 14.5" overall with bodies and bells. We run a Megasquirt ecu with AEM WB with the gauge facing me in the car. Air Fuels are set at 11.5 to 12.0, we are running rich to minimize detonation. Once the detonation is under control, we will lean it down.

The engine pulls hard from 3,500 to 9,500 in second and on short tracks in third. At Mosport what happens is that it will come out of 5b hard in second and I shift at about 8,500 rpm (data logging shows that by the time I finish shifting its pulling close to 9,000. After a couple of laps, it starts farther up the back Andretti Straight. The straight is 3/4's of a mile long and all up hill. What happens is that the car starts a light rattle, that disappears when I lift off the throttle. It then rattles harder and starts to detonate under load. The noise abates a bit if I keep it at full throttle, but it is still there. I hear the noise coming from the firewall on the passenger side. It is also loud enough to hear clearly over the motor, through my helmet, balaclave and earplugs.

After a lap or 2 of this, it then starts to rattle on every hard throttle pull. When that happens, if I left off the throttle and only use about 1/4 throttle, I can drive the car without rattling and carry the rpm right up to 8,500 with no rattling/ detonation. I have been around race cars for over 30 years and its a classic detonation/ preignition noise.

The odd thing is that it only happens at Mosport (which is like Road Atlanta) and seems to be time and load related versus temp or rpm related. At Shannonville, which is a tighter track with the car in second and third only. I run Shell Street Premium fuel as it contains no ethanol and is 91 octane.

The only doubt I have on it being detonation, is that the engine has run like this for about 5 hours with no issues or loss of compression and I would expect it to have blown up by now. If it is detonation, which I believe, I would then believe that Joe at RPM builds the strongest motors in the world, LOL.

What else do you need?

Eric

peejay

I can attest that prolonged detonation will result in trashed corner seal springs.

Are you SURE it's detonation? I ask only because I finally found the source of my own rattle. The exhaust system grows so much when hot that the tail end hits things.

What are your oil temps like?

Is there any chance that you have ignition crosstalk under load?

23Racer

OIl temps were about 180 degrees, water started at 210 then came down to 190ish and it still rattled. It really sounds like detonation, but the engine still has good compression, so I am going on a dyno to see if I can replicate it.

Eric

j9fd3s

iTrader: (3)

+1! i did it too, the rotaries are fragile, it only ran like that for 2-3 years before it died.....

anyways, since its related to the length of the pull down the straight, what spark plugs are you using?

high power + long pulls = you need the racing spark plugs.

since you're in there though, this is a good time to look at spark plug wire routing, the trailing wires should be separate from each other and the leadings. the leadings fire together, so it doesn't matter if they crossfire.

it also would be good to verify TDC, and the marks on the pulley, i've got a stack of pulleys at the shop and i compared em and they are all the same, so you're probably fine, but it doesn't hurt to check. you should also verify the ECU too, when it says -5BTDC is it actually -5BTDC.

23Racer

I am using the NGK Race Plugs 11.5 cold (only ones they sell in Canada). I will look at the plug wires to make sure. I am using Taylor 10mm race wires, but I will check it out. I am also going to reconfirm the TDC point of the rotor to the CAS. It could be the issue, but man that would tick me off if it was.

Also, when the engine is rattling, if I breathe the throttle the rattling dies off or goes away. When I am at part throttle and it starts to rattle, if I open the throttles more the rattling changes to knocking. If I reduce the throttle opening to just about 1/4 throttle, the car will rev out to about 9,000 rpm with no issues other than a really slow rate of acceleration.

Thanks for the tips and things to check. I am making a list for next time I am in the shop.

Eric

Kentetsu

I'll admit that I'm a lowly 12a guy, and most of this discussion is over my head. There is one thing that sticks out for me though, and that's the fact that you don't have this issue in the lower gears.

The biggest difference between the lower gears and the higher would be fuel quantity. So, if there were a restriction in your fuel flow, you may still have good performance in the lower gears but begin starving in higher gears. We see this all the time on 1st gens with clogged fuel filters.

But having said that, now you will probably tell me that you have a magical gadget that monitors your air/fuel ratios and everything is fine. Thought I'd throw it out there anyway, just in case.

Best of luck...




.

peejay

It's called EFI. Carbureted cars can run short bursts with an insufficient fuel system because the fuel bowls hold a certain amount of fuel. (Enough for the engine to idle for about 5 minutes with no fuel pump, with the Nikki)

With EFI, if you have enough fuel system for 1st, you have enough for 5th.

It definitely sounds like it's a heat related issue. All the same, I'd seriously look into the possibility of the ignition system crossfiring.

Also, as rich as you're running it, I wonder how much carbon there is on the rotors.

23Racer

"Also, as rich as you're running it, I wonder how much carbon there is on the rotors."

Interesting idea. I will try to chemical clean the rotors. Anyone with a good way to do this? I was wondering that myself as on old piston engine cars it can cause these issues. Great idea.

Eric

j9fd3s

iTrader: (3)

the car's i've had pinging/detonation problems on had different causes.

1. my 20B, this one was easy, somehow i missed the 4000rpm timing map, and it would ping when it hit the default map@4000, SCARY when the 3 rotor pings!

2. my old GSL-SE. with the S4 engine and Rb exhaust it would just run out of fuel on the top end, the PROBLEM WAS WORSE IN THE HIGHER GEARS. it actually would go thru the pinging and stop running it was so lean up top. i put a bigger fuel pump in, and tweaked the afm, but i think i needed more injector

3. my friend had an FD he was working on, and it would ping a little, it was the spark plug wires, for some reason when the FD needs plug wires it pings? i've seen it since on a few different ones, FC's usually just misfire up top.

4. steves car. this one pinged like crazy, it sounded BAD. it turned out that we had left a big vacuum leak switching over to the haltech, no mapping would fix it. i think i made an ACV gasket out of a soda can (no holes), and THAT fixed it

i should point out that the 20B was fine, it was killed later during a rebuild, RIP #246. the GSL-SE went to track days for a couple years pinging like that, and it died in a "i was drifting it at the rev limiter" session. it had no rev limiter

no idea about the FD, and steves car is fine.

23Racer

Other interesting things to try. I have thought about the car running out of fuel, but the Air Fuels show it is running in 11.5 - 12.5 range still, even while it is pinging. It also doesn't explain why the problem gets worse the longer we run the car, then after it cools off overnight, its like nothing was wrong.

Could be a vacuum leak, like the one you are talking about. I am going through the whole car again to make sure it is sealed up.

I am also going to look at the plug wires again and route them differently or try a different set. Could be the issue as well.

I am leaning towards carbon build up that gets hotter and hotter until it starts to act like a glow plug. I am going to try the water clean out as well.

Lots of very good ideas. Its driving me nuts as the car didn't do it initially, then started doing it only at Mosport. Works great in lower gears and at shorter tracks that don't have sustained high gear (3rd and 4th) loads.

Eric

j9fd3s

iTrader: (3)

yeah i think if you check the car out it'll at least narrow down the list.

23Racer

I am working out the details. Last night was the first time I had any free time to work on the car. The first thing I wanted to check was the relative position of the CAS. I pulled the cover off the CAS and rotated the eccentric shaft to the -5 BTDC mark and everyhting didn't look exactly correct. My CAS was all the way to the left end and it should have been in the center if the timing was going to be correct. I called up Dave to find out why the orientation of the spokes of the upper trigger arms didn't look like the required Megasquirt plunge and he said that our Megasquirt had the extra signal conditioning circuit and it should be plunged like a stock RX7.

Pulled out the CAS, aligned the marks again plunged the CAS and oriented it so that the centre of the adjustment the base point for the lock down nut. Crossed my fingers and tried to start the car.

The car fired instantly (after sitting for 2 weeks), settled at an easy idle at around 1200 rpm (about 200 rpm lower), the air fuels changed from a steady 11.5 - 12.5 before to a new range of 12.5 to low 13's and the car developed a bridge port lope at idle for the first time. As well there was a lot less smoke out of the tailpipe. I shut the car down, felt a bit sick and went inside. If the whole issue is that we were 1 tooth out on the CAS I am going to hurl. If it is, it also shows why you should always check everything yourself. I have had about 6 peoples hands on the car trying to work out issues and anybody could have installed the CAS wrong. So if that was the cause, I find it very interesting that the Air Fuels would change so dramatically, it would develop a lope and the exhaust would be cleaner. Going to take it over to a buddies car dealership this weekend to do the water treatment and set up the timing once and for sure in a place where I can let the car run for a while.

Eric

23Racer

"it also would be good to verify TDC, and the marks on the pulley, i've got a stack of pulleys at the shop and i compared em and they are all the same, so you're probably fine, but it doesn't hurt to check. you should also verify the ECU too, when it says -5BTDC is it actually -5BTDC."

Fundimentals, always fundimentals. If this fixed it I feel like going outside and banging my head against a wall for about 5 hours..........

Eric (with a sore head)

Roen

iTrader: (2)

There's a tech article floating around somewhere on the internet for water injection cleaning (not AI) the second gen rotary engine in an effot to abate carbon. May be of use.

j9fd3s

iTrader: (3)

yes but so far this looks like the fix is A) possible and b) kind of simple

23Racer

True and the motor is still okay with decent compression and pressures, so I should be happy.

I am still going to go and steam clean my rotors and make sure everything is held down properly. Then I am going to a local dyno that has the Mosport uphill straight simulated and run a bunch of trial runs with the car hot. If all works out correctly, then I will do a couple of HP and torque pulls to set timing and fueling. Only after all is okay on the dyno will I go to a test day and try it out. The next test is October 22nd, so I need to get cracking.

After the test day I will build the cold airbox, put the bumpsteered front spindles on, put the 3 way adjustable struts in, TII front brakes and the new splitter to get ready for next year. These are all winter projects for the RX7. After the RX7 is ready, I need to get to work on the Cougar.... I need more time in the week.

Eric

peejay

Sounds like when I was hurting engines last year partially because the Racing Beat single groove eccentric pulley was marked 0/12.5/25 and I thought it was 0/10/20.

Live and learn!

33 degrees of timing is too much, with a half bridge, locked timing, and 87 octane