Intake temp and reduced BHP...
 

I had my first service on my Type 20 today and Powerstation ran it on the dyno for a map tweak.. One question I forgot to ask was;

What difference will a 10 degree air temperature make to the BHP figures? Is it a linear increase as the temp drops?

My top figures were 315 BHP and 308 Ft Lbs, with an intake temp of 27.5 degrees.. It was very warm in the Dyno room and the various fans were on full, but the temp was probably about 10 degrees higher than some of the other figures I saw on other runs...

Will a reduction of 10 degrees make a big or negligible difference?

The rise in air temp will make a difference. But rolling road figures are usually corrected for standard air temp and pressure (20 degC).

Thanks mate..

It was just a map tweak rather than a full Dyno session and they did 3 quick runs to get the Torque up and smooth rather than outright BHP but the adjustments didn't seem corrected. They did say that cooler temps would have resuted in higher figures....

All the readings I saw were with current temp and the adjustments made slight deviations to what appeared to be the true unajusted Power & Torque figures .. All the other graphs seemed to be at 17 degrees.. So I'm not entirely sure..

It's worse for turbo cars. It's a double whammy effect. First the air isn't as cool as normal, then it's compressed by the turbo, causing it to be hot, then the i/c can't remove the heat as adequately as in cool air.

lose, lose :(

Alan,
How did you measure the intake temps?

These arnt the important temps though...... it's the charge temps after the intercooler you want to be concerned with (although they are linked, but as the later TMIC is very efficient it is not as much as an issue than others).

I was in the dyno cell all day today non stop (must of completed about 10 re-maps and many, many, many runs)

If you want to go the mod route, I believe you may be presented with a number of options! ;) :)

Regards,
Shaun.

Shaun.. I've no idea how it was done.. The 3 runs were quick and only to tweak it after the service so I'm not sure how much of the whole dyno process was completed or concentrated on.

Plus, there was a lovelly track car on the dyno from Loaded Gunn Racing. The guys had to move it off in between a misfire check to get mine on.. so I was concious of holding these guys up seeing that they'd paid for the day..

I do know the temp that was pointed out to me was 10 Degress higher than the other runs shown and within 1/2 degree (28) of the ECU starting to retard the car due to the intake temperature... So this could have been charge temps???

FYI Jap Performence mag have an article explaining thepurpose of the I/C this month. They said (I think) a 1 degree increase equates to 4bhp loss on most turbo cars. Can't imagine this is an accurate rule though, or that it would be a linear relationship

Alan,

I have the secs monitor fitted to my car, a SPA gauge which measures temp after intercooler going into throttle body (now does not work after trackday, must have overheated :rolleyes: ).

Anyway, typically the temp into the throttle is normally about 3 degrees above the intake temp seen by SECS/ECU.

IIRC, if the ECU sees 35 degrees on the intake then it will retard the ignition and therefore power will be down.

I remember talking to Iain when he took his Type25 and Darren had his Type25 at Scoobyshootout last year. Both cars had over 35 degrees and due to that the power was pulled back by the timing. The both still managed around 12.5 second qtr's though lol!

On a recent trackday at croft my car was suffering with the heat and it felt down on power.

Just wait until winter :cool:

Damian.

Both of which support the lower powers than I would have expected.. (plus it is only 1,500 miles old.. and a little tight..)

However the Linear graph seems a little optimitisic considering the 10 degrees would mean a healthy 355 BHP.. :D

Plus, seeing some engineering charts that take into consideration air density, moisture levels, height above sea level etc etc etc I'm sure it would be a curve of some description..

Good debate though! :D

Hi Alan ... my T20 was measured at 316BHP in 27.5 degrees just after my 1K service. I was told by Powerstation that they would expect somewhere between 300 and 320 and that anything round about 315 was very good. Again they emphsised that if it was cooler, the figures would be at least another 10BHP higher.

Its all gobbledigook to me anyway ... it's bl**dy fast whatever its BHP !! I have to remind myself to keep looking at the speedo when I'm on the Mway as I feel as though I'm daudling .. and the speedo aledges that I'm going over 110 most of the time ..... must be a speedo problem :norty:

i hope it is 1degree is 4bhp or similar because mine was 268bhp with a full decat and that isnt even above standard. fuelling and boost spot on! it was baking and at power engineering....

As I've said, my BHP was backed off to give more boost.. but the heat definately makes a difference..

No issues though, it drives bloody well... :D