silver1.3

In every engine I've had there is some HP loss once the engine is warmed up. But is it me or does the rotary engine seem even more at a loss of HP once its at full operating temp. Seems like im loosing 15-20 hp.

RX Renesis

could it be that ur living in a hotter climate?

expo1

Please try to logically explain why any engine, let alone ours would give peak performance while cold? I have done track days when it was over 90 with no problems, hell the fan doesn't even come on after shutdown when I did that.

Psylence

HP loss? How 'bout the MPG loss that every internal combustion engine gets until it's up to operating temp?

Fanman

It's called heatsoak. It effects every engine. Our car lost 20 hp when we drove off the lot (not really 238 hp), so it depends on where you think you are starting from.

expo1

I stand corrected, I have heard owners of FI cars talk about heatsoak, but I don’t hear that much at the track form N/A owners. Maybe if the original poster mentioned heatsoak and what he was doing when he believes his car is losing HP I would have posted something else. The way I read it was “ when my car is warmed up and just driving around town I feel a HP loss”

10kRPMS

All the K&N filters are sucking hot air......LOL

silver1.3

I was simply trying to see if I was the only one experiencing this to such a degree. Yes I do live in the south, and I know its called heat soak, but I was interested in if it is more dramatic with our cars than say a piston engine or is what Im experiencing normal. With all the flashes I have its hard knowing what is normal and what is not anymore.

I have the infamous "marble in the can" sound but it only happens when the car is under load and at the rpm the VDAIS operates at. I didn't know if this loss of power was related. I called my Mazda dealer today and asked how much a compression check would cost and they said $60. I might get it done to ease my mind.

One thought I had that if the "marble in the can"sound was pinging then it seems as least that it cant be loss of compression (thus loss of power) b/c if you loose compression I dont think you would have preignition - but thats just my guess I might be wrong.

Fanman

Are you using 91+ octane fuel ? I live in Los Angeles. Very hot area as well. Have had no issue with detonation/hesitation. Have always used 91 though. Never have loss of compression.

A few early RX8's had some issues in the Arizona area with stalling/overheating. Not sure what flash your are on, may want to take it in.

RotaryNoob

My car feels more powerful while its cold. Don't get me wrong, I don't go redlining until its up to operating temps but the first couple of hard pulls just after it hits operating temps seem to be much stronger than when its been driven for a while.

I think all cars run better cold but the rotary does give much more heat than a standard piston engine so it is very possible.

MrJynx

i thought all engines run best between 60-70deg with no humidity.. I don't think it's an issue with just the rotary, but all vehicles.

Fanman

I think the original posters question is moreso does the rotary lose even more power then normal in hot weather.

Nemesis8

iTrader: (3)

Isn't there a rule of thumb about intake air temp vs. HP available?

Blue87Sport

Anyone remember a thread about the Racing Beat open house at Sevenstock last year where they were showing their ECU test bench? RB could alter various ECU input parameters, such as coolant temperature, and see how the ECU changed the fuel/timing outputs. IIRC, changing the coolant temperature had a significant impact on performance. I couldn't find the thread via a search. Anybody else remember this or am I going senile?

KYLiquid

i feel like my car drives its best after its been running/driving for about 20 mins...when everything from the engine to the diff is up to temp.

I do notice that when the car is pushed really hard on hot days, and starts to get really hot...that the performance suffers.

The car monitors cat. temp as well as coolant temp, and will adjust the engine timing/air-fuel accordly.

the hotter the car gets, the more fuel it runs (to cool down the combustion and in turn the motor/cat) and it also starts to make the timing less agressive again to cool things down.

could this be what your feeling.

RexApex

Dyno? G-tech? or just "feel"?
--R.

silver1.3

actually, yes, this is what I think I am loosing. The only other thing might be a compression. Mind you temps are in the 94 deg. and 90% humidity too.

loco-8

Cooler air should give more hp, warmer air less. Sure you're all familiar with the percentage of hp loss after adding a turbo, because hot air is used, convection allow other components to stay warm, creating a climate for the intake air to get warmer as well, and yaddy yaddy. Intercoolers are used to try to combat that. Cooler air allows energy to build up before ignition compared to warmer air. So, the cooler, the more hp and "feel" of hp. What silver1.3's noting.
On hotter days, the RX-8 sometimes feels like it loses more "umph" compared to regular piston engines, but not always. Probably not enough to make it (statistically) significantly different.

KYLiquid

i dont see how you would be loosing compression only when hot, there would have to be a leak somewhere to have compression loss, so you would notice it all the time.

The car opperates best when all the drivetrain (trany, engine, diff) are at normal operating temp...as those temps increase....the engine becomes less efficent and makes less power output...what you feel (since it sounds like its similar weather to here in central FL) is that the power drops off as you push the car harder.

Give the car a time to cruise around at speed (say 50mph in 6th gear) so your getting good airflow over the radiator/oil coolers but not making a lot of extra heat from high rpms. a few mins like this should help.

I dont yet have my gauges hooked up to read oil/water temps (not the stock water temp gauge...its pretty useless) but I do have a thermo in the dash airvent (to measure ac output temp) it reads from 0*F-280*F, I notice that if I have the heater on (outside 'fresh' air setting) and the blower on full speed (4) that the output air is 140*F, when I push the car, It will get as high as 190*F thats 50*F increase, keeping in mind thats just telling me the temp of the air coming off the 'radiator' i assume that temp under the hood is getting up to around the same ~200*F and the coolant/oil temps must be climing to 220*F-230*F.......very very hot....it can quickly 'heat-soak' the intake box, even with how fast the air flows thru it, when outside air is already 90*F in the trip from the inlet to the intake port on the motor it can easily pick up 30+ *F

silver1.3

i agree completely, I should have noted that even when its cool I don't get that extra "ummmf" im use to, that's whats giving me concern about compression. Yesterday I pulled up my drive (on a slight incline) and the car almost died - like there wasn't enough power to pull it up.

I took the car intoday for the recall work (which got done, and Im about to pick it up) the tank and ball joint stuff. I asked that they do a compression check (i would pay for it, it will be $60) but their compression checker is broke. They said they would call me when the one they ordered came in.