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Hi Guys,

My motor is able to keep up with the others around me for a couple of laps but then seems to lose hp. The times drop off slowly as the laps go on. I've checked my temperature guage which reads fine so I'm stumped for ideas. On the weekend, I managed to do my fastest lap on lap 2 of every race which is unlike me. I tend to go faster as the laps go on.

If you take tyres and driver out of the equation would it be possible to lose hp as the motor heats up and what would be your recommended solution? I know the obvious answer would be to get a bigger radiator but like I said the temp reads fine. Any other suggestion?

Regards - John

Btw, my car is an NA6.

Intake temps could cause reduced power, perhaps after the couple of laps it's soaking in? - wouldn't cause a change to the temp gauge.

Also brakes, perhaps they're getting a bit hot and not working as well as the start.




I'd still put money on driver fatigue though.

slipping clutch

What ECU are you running? Maybe it is pulling timing as the intake temps rise?

If possible try to take a datalog.

Could be anything from track temp, car temp, driver skill, tyres going off, engine problem, or just plain perception.

Hey John, heat soak? Any issues with the carbs?

You can't even begin to answer this until you understand exactly where you're losing time. Is it braking points, line changes, brake performance, corner entry speeds, mid-corner speeds, corner exit speeds, acceleration performance, top speeds or all of these?

You have to be logging and comparing. If you haven't got dedicated gear already then a decent 10Hz GPS receiver feeding the Racechrono app on Android or old Nokia or Harry's Laptimer on iPhone will do the job.

Just because the temp gauge doesn't say it's getting hot doesn't mean it isn't. They have a know dead spot where they read "normal". Still wouldn't have expected it to make that much of a difference.

Please tell me your not running carbs?

sailaholic wrote:Just because the temp gauge doesn't say it's getting hot doesn't mean it isn't. They have a know dead spot where they read "normal". Still wouldn't have expected it to make that much of a difference.

Please tell me your not running carbs?

Um yes. Not my doing though, previous owner thought it was a cheaper way of getting a throttle body affect. I've pursisted with it just because it's different.

Ok, so that's fairly important as it now begs the question what's the filter / intake setup. If its just old school awesome filter socks then your intake temps might be getting much higher robbing you of power.

Also filter socks rob power all the time at high rpm assuming you are running nice velocity stacks.

sailaholic wrote:If its just old school awesome filter socks then your intake temps might be getting much higher robbing you of power.

For reference I have been tracking the engine bay temp and the intake air temps in my NA6. I have put a sensor near the charcoal canister and it has been reading about 80 c and the intake temp is about 29 c (Mania CAI).

I'll have some more data on Saturday afternoon if interested, hopefully I will have an air temp as well.

Magpie, that's interesting! I have not noticed my ait being that high except if sitting ideling. Has been about mid 40 ish but sensor is in a dodgy location, about where factory coil packs would sit. I would have expected it to read higher there.

I calibrated my sensors the other day so they should be accurate, however I will recalibrate before Saturday. I calibrate them with hot/cold water, put the sensor in hot water note the temp on a thermometer and note the output voltage, repeat with iced water. I'm using 5 volt sensors so the temp/voltage is linear.

Magpie, very interesting. So intake temps of 80 degrees would certainly rode hp I would assume. My issue is carbs have been around for so long why are we now realising a heat issue. Maybe I need to make a cold air box feeding the carbs or find a way to remove heat from the engine bay more effectively of both.

Thanks to everyone for their input.

Regards - John

That's interesting - carbs! I think check your tuning. Maybe the carbs aren't quite right (fuel could be starved, evaporating, heat as discussed, etc).