It has been brought to my attn that some(most?) might think that I am incorrect(read slower on next run) by letting the 8 idle for awhile after a run while spraying oil coolers and radiator(AC) with water and having AC on with heater controls midrange.

I think shutting the car off immediately after a run and spraying will result in less HP at start of next run unless car really does have a long wait before next run(15+ minutes)

Why do I think the first way is better?

Because the inside of the rotary is cooled by oil, not coolant(there is no coolant in the middle of the engine) and keeping the fluids circulating while cooling them will actually decrease heat that is stored in motor versus just shutting off the car after a hard run.
I have not seen how the cooling system works in regards to intake coolant circulation on the 8 but most(all so far) rotaries have coolant that circulates through some part of the intake system to prevent icing and shutting off a hot engine will cause the super heated coolant to rise up into the intake which I think is bad for HP production. Does the 8 have a thermostat shut off for this coolant flow when hot? I have not looked at the FSM on this but it could have a shutoff. The oil cooling system also usually has a thermostat on the later models of the rotary.
Keeping the fuel pump on and circulating could add some benefit too although I have not seen the FSM on this system either....

How do I find out if I am correct on HP/TQ thing?

I will dyno Shelbi's car when her exhaust is done and try out both ways.

3 consecutive runs for baseline, then do a 5 minute wait with motor off with spraying and engine cover off/hood up/key on with A/C button pushed then do a dyno pull.
Many just shut the car off and do not worry about tricking the fans on which I also think is a mistake.

Then I will do a 2-3 minute idle/engine running spraying with A/C on/engine cover off etc. then 2-3 minute wait then do a pull.
I might even try out a pull after not turning motor off at all..just idling for 5 minutes with no spraying at all if the dyno guys are in a good mood....

I would let the car sit off for longer than 5 minutes off but dyno time ain't cheap.

Any predictions on which of the last 2 pulls will make more hp/tq?
I suspect most will say the "motor off" way.

Kinda hoping to have someone chime in that has done a test similar to this.

Lots of my car set up/autox stuff is different than the "norm"(like smallish front bars/lower shock rebound settings) so I want to see if I am off base on this or if it even matters at all + I want to see how the new exhaust and wires do when she gets the exhaust/previous straight pipe was getting a little high rpm missing so I am hoping wires solve it.....

FM

 

I didn't read all your long post Mike but I can tell you that Ron & Joe tried your way on Sat at the Denver tour and the car was progressively SLOWER each run (look @ Ron's dirty first run w/ cold car/cold tires vs. his & Joe's third runs), tried the old fashioned way (shut off car, but turn on accessory AC fan) after first runs Sun and the car was MUCH BETTER.

 

Honestly, Mike, I haven't looked at the results. I'm just going off what Ron told me by phone. They tried your way and hated it, the car felt horrible, etc, they drove significantly better but the times didn't really reflect what they thought the improvements were. They said that shutting the car off between runs Sun. was a significantly better option than leaving it running.

Put it this way - I didn't ask about this "test" at all, because I didn't know they were even doing it. This was something Ron thought was important enough to mention to me w/o me asking, even pointing out it was your recommendation, so I think it's pretty significant.

 

Mike,

As I told you on the phone, it wasn't a "progressive" slowing as Annie said.

My first run Saturday was 2 SECONDS faster than Joe's first run and 1.7 SECONDS faster than my second run. Even my 3rd run was 9/10ths slower than my first run and each run felt better. The cones I hit in my opinion gained me next to nothing. I was convinced that I was going to be able to take off over a second from my first run when I first came in. We were spraying the heck out of the tires and I think we got them pretty darned cool after each run. If I had made a big mistake on my 2nd and 3rd runs I could see slowing down a couple of 10ths, but not being able to come within 9/10ths of my first run was definitely not driving. Each run felt better than the previous.

Sunday I went first and we did the leave the car running thing after my first run. Joe was 1.2 SECONDS slower. You know as well as I do that Joe and I are usually pretty darned consistent with each other. At this point after seeing his time, I noted to Anna that I didn't agree with leaving the car running. She was of the same opinion, so I told Joe I'd rather turn the car off but leave the a/c running with the ignition on to keep the fan running. We did this, and I took off 2/10ths on my second run and Joe sped up quite a bit on his second run. My 3rd run shaved off another 5/10ths and Joe was ultimately 1.1 seconds faster than his first run.

FWIW, on Saturday my first run had me hitting the buzzer prior to the finish line, while I couldn't even get to it after the finish line on my subsequent runs. Sunday I only hit the buzzer once and that was on my 3rd run.

While I'm half curious as to what your dyno results show, my real world results show that leaving the car running keeps the heat in the engine and slows the car down. I understand your philosophy, but it didn't work in my opinion.

Also note that the temperatures in Denver were in the 90's both days when we ran....

Ron

 

I can support Ron's theory in this...

Same thing with the Devens tour. Look at my times.

Saturday, my 1st run was fastest then slower each run. I kept the car running between heats.

2nd day, much nicer out... hotter yes, but I didn't keep the car running. Improved 1/2 second each run.

I hardly ever go slower on my consecutive runs.. unless the car was running.

Even the last NER event, I had 3 re-runs in a row with a 5 min break between them. Not only did I overheat the Kumhos and go slower, the car was not as fast as it was after my 1st three runs (where I had time for the car to cool off).

I'd agree... shutting it off seems like the right thing to do.

 

I spoke with Mazda about heat concerns with the motor. The guys told me that the T2 RX8s run with no cooling mods and dont have a problem. The RX8 already runs very fat and to cool it down will only make it worse, the real power comes when the car leans out.

I try to treat it like the RX7tt, I turn the heater on high and pop the hood. First thing I spray is the oil coolers, spray the drivers side extra as it is the first in line, then the tires. Once the fan shuts off I turn off the car and spray the oil coolers some more.

As far as running the AC, I have never been a fan :D of that... On the Vette with a real temp gauge you could seem the temp go up when you turned on the AC. Even though you set the temp to hot and the 2nd fan came on the extra drag from the AC unit drove the temp up a bit.

I think you have more to loose from the tires being to hot than the motor on those hot two driver days.

I hope we can see something on the dyno runs, as the RX8 seems to give funny charts.

Remember to use 5th gear this time.

 

Wait the fast guys were in CO and you still could not win PAX.

Better change that name..... Mid-Pack Mike. :D

 

I was wondering about that too.
I wonder, even after spraying tires down, is anyone taking tire temps [probe-type], and is that even a decent indicator of what the tire situation is on the inside?

 

Mike beat Karl Coleman in a Mini and Kevin Dietz in the Fordahl Porsche at the Sportscar Spectacular this past weekend. I think he can still keep the name Fast Mike. Mid Pack Mike does have a nice ring to it though.

I think setting up a solid test procedure to test your theory is a good idea Mike, however doing it on a dyno can be somewhat difficult. You have the expense and everything to deal with. Setting up accurate water and oil temp gauges then testing the car and keeping records in a variety of conditions over time I think would be the best way to test out your ideas.

 

I s'pose any of those are better than %$^@%#$. :D

 

your RX-8 will run much better on 87 octane fuel too ... and be sure to click your heals three times and repeat "I wish I were first, I wish I were first, I wish I were first" and you'll have a Topeka championship in no time, Dorothy

 

There's a flaw in your plan... while the 87 is a known proven entity, 'wishing' aint going to do you a heck of a lot of good in Topeka toto. :D

--kC
(Hmm... we need a Nationals smack talk thread)

 

which is why you have to click your heels

you guys from New England are pretty slow...if you aren't careful, we'll think you're from Canada, eh? :p

 

BTW, you did have the fan set to the #3 fan position, the A/C temp control set to the middle of the blue area, recirc mode vent position, and you're foot holding the gas pedal to maintain 3000 rpm, right? It only works with those specific settings ...

 

I leave the AC on during my run.. it sucks air into the car and out the windows... pulling the car through the air. I just haven't figured out to have it stop from shutting off at more than 90% throttle... I need it most when the car as at WOT.

 

Oh, so you're a windows-open driver, so you must not be using the helium trick. (Filling the car with helium before a run to make the car lighter and faster, only drawback is not being able to talk to the timeslips person at the end of the course.)

 

Actually.. I did try that once.. while listening to Tom Sawyer by Rush on my run.

For some reason, when I got my time-slip, the guy thought I was Geddy Lee. Honored, but I stopped the helium shortly after that.

 

I also thought about exhaust vectoring.....

 

All kidding aside, does 87 octane vs 91-93 octane make a difference in AutoX?

I am just getting back into AutoX (with my 8) after a very long absence from the sport. I usually run 87 on the street. At my first event this year, I tried running premium and really bogged on the launch. I verified that the DCS/TCS was fully off and I don't think it was user error. My first guess was that the ECU had the fuel trim settings expecting 87 and couldn't adjust to take advantage of higher octane timing. Opinions?

Otherwise, keep those AutoX secrets coming. Us newbs are eating them up.

 

A couple thoughts on cooling.

The car has a thermostat. That thermostat will stay open only when the coolant is above a certain temp. It does this to help the engine warm up more quickly. If you're idling the car while trying to cool it, and manage to cool the coolant in the radiator below the thermo's opening temp (80C?) the thermo will work against you and close. This is pretty unlikely to happen, but possible I guess.

Secondly, just think for a moment about engery in vs energy out. If the car is off and you're spraying it down, all you're doing is removing heat. If the car is running, there's combustion going on, which is adding heat. Granted, with the car off you're spraying is mostly on the radiator and oil cooler, fluids that aren't in the engine, but think about what happens when you turn the engine back on. You've got a huge rush of cooled fluids going into the engine which will probably bring the temp down very quickly. Unless you manage to get the radiator cool enough that additional spraying won't cool it further, it seems to make sense that spraying with the engine off is more effective. If you do reach that point, I would idle the car for about 10-20 seconds to get the hot fluid out to the radiator, then start spraying again.

The only reasons I can see for spraying with the engine on is to (1) more gradually cool the engine vs. sending a rush of colder fluids upon restart, and (2) for turbo applications where you're dealing with temps so high that you need to keep the oil flowing until the turbo cools down so that it doesn't burn up in the turbo.

Jason, I'm not sure how the ECU controls fuel in this car, but i would think that once it's out of cold-start mode, it'd run leaner the colder it is? Doesn't every motor make more power in cold weather, the air is just denser?

Totally agree on tires being more important. It's unfortunate that codriving is beginning to be detrimental in some circumstances.

 

You know what I may think your making some sense. I'll drive my car to the car wash and then when I leave it just feels slower. LOL

 

filling your tires up with water will help keep them planted to the pavement better ....

 

Cooler cars run richer.... A hot motor will lean out. Yes in cool weather you will make more power because the air is denser not because the motor is cooler.

 

that's why you have to retune the jets and set the bowl fuel level height just right

 

You should do it while listening to Red Barchetta. More of a car song!