What's a reasonable intake differential pressure?

[iacs_hsv]

Looking through my logs of the runs I did at Shakespeare, I see that my WOT MAP is repeatable @ 96kPa. Logging MAP with engine off reads 101kPa - so the question: is 5kPa a reasonable differential pressure at WOT, or should I be aiming to improve on this as Ringram is exploring?

Thoughts...

Edited by iacs_hsv on Friday 17th July 12:46

[ringram]

iacs_hsv said:

Looking through my logs of the runs I did at Shakespeare, I see that my WOT MAP is repeatable @ 96kPa. Logging MAP with engine off reads 101kPa - so the question: is 5kPa a reasonable differential pressure at WOT, or should I be aiming to improve on this as Ringram is exploring?

Thoughts...

100% you should! You should aim for no restriction. If you are reading less than atmospheric then you are losing power. Its almost a direct relationship. (ie) 5% less than atmos will be around 5% less power give or take.

The map sensor is at the rear in earlier intakes and front in later ones. Usually its throttle or air intake ducting that causes the problem.

I was getting 94-96kpa at times. So this weekend its throttle hacking time, plus Im going back to my otrcai.
FWIW the stock intake wasnt much worse than the otraci reading about 1-2kpa less. Therefore I think I might need more throttle opening.

Aim for zero loss, but Id say 2kpa was marginally acceptable

[iacs_hsv]

Thanks Richard, I'm guessing the K&N is dropping a couple of kPa, plus I'm not running SD at the moment so maybe a 85mm MAF may help.

I'm going to experiment by dropping into SD and disconnecting zip tube, MAF etc from the TB, then doing a couple of WOT runs to see what I get. If it's not changed much then it must be the throttle body...

Will post up test results.

[ringram]

Yeah I know guys on the dyno take the whole lot off and run bare TB for a run to see what happens as a process of elimination.
Not that you want to do that without a filter for much if at all. But in a dyno room it would be ok.

You can go into mafless mode just by unhooking the MAF, but fueling might be out so check AFR etc. Also unless you have a custom OS or high octane table copied over the low one it will drop into the low octane table.

Ill probably do the same next dyno trip as Id love to eliminate any restriction to free up some more power.

[stevieturbo]

There is one easy way to improve that kpa reading :P

[granada203028]

What sort of pressure drop do you get across the air filter? Any idea how much this increases as the air filter gets dirty. Are K & Ns genuinely better? Another thread high lights that the paper one is quite cheap so you could replace it 5 times for the price of a K & N.

[ringram]

Plus its more effective.
Mine was pretty dirty and like I say only 1 to 2kpa worse than my otrcai K&N.
But I didnt measure the pressure drop across the filter only the manifold vacuum. I dont have the kit for that.
Over to you for that Mr Granada

[stevieturbo]

Some reading.

http://www.autospeed.com/cms/A_0629/article.html

http://www.autospeed.com/cms/A_0637/article.html

http://www.autospeed.com/cms/A_107824/article.html

[iacs_hsv]

ringram said:

Yeah I know guys on the dyno take the whole lot off and run bare TB for a run to see what happens as a process of elimination.
Not that you want to do that without a filter for much if at all. But in a dyno room it would be ok.

You can go into mafless mode just by unhooking the MAF, but fueling might be out so check AFR etc. Also unless you have a custom OS or high octane table copied over the low one it will drop into the low octane table.

Ill probably do the same next dyno trip as Id love to eliminate any restriction to free up some more power.

I'm running a custom HPT RTT OS with HO = LO spark, plus MAF Fail Freq = 0 to avoid DTC. Occasionaly run SD to check VE map fuelling, but I find I get better control running with the MAF, so this is my default configuration.

I wasn't planning any open TB runs on the road, I'll do up at Powerstation.

[ringram]

Nice with the RTT for dialing in MBT for spark mate.
Good to see someone else rolling their own tune. It would be interesting to see if your maf and/or air intake is losing you power.
If its the stock MAF you should at least upgrade to an 85mm one.

[iacs_hsv]

ringram said:

Nice with the RTT for dialing in MBT for spark mate.
Good to see someone else rolling their own tune. It would be interesting to see if your maf and/or air intake is losing you power.
If its the stock MAF you should at least upgrade to an 85mm one.

Confirmed - stock MAF at the moment, abeit de-screened with a bit of a polish - plus the inevitable re-cal of the curve...

[iacs_hsv]

It would be interesting to get hold of another small MAP sensor which puts out 0-5v. I could then wire into one the AIs on my interface and take some readings in the air box lid, after the MAF etc...

Mmmm, ebay calls!