9psi JRSC boost drop (10 --> 7psi) when VTEC engages - Honda Prelude Forum

NoRice4U · 04-06-2006, 02:46 PM

I have 550cc injectors + p28 + Hondata 200b and my car kept experiencing a 3 psi drop in boost when VTEC engages while getting it dyno tuned. My tuner tightened all my belts but I'm going tomorrow to the mechanic that installed my SC and get it everything double checked. Any other ideas of what might be the cause of this problem? Thanks!

edit: I got about 225whp (SAE) which is kind of low for 9psi

My mods are
AEM CAI
AEM Pulleys
Mugen Header
Greddy Evo Exhaust
MSD Ignition + MSD SS Blaster Coil
ACT Clutch + Fidanza Flywheel

edit 2: My AWESOME (not) dyno graph with boost loss. A/F hovered around 12.5

http://s54.yousendit.com/d.aspx?id=0...S370D6ZVCEQQ0N

Daemione · 04-06-2006, 03:36 PM

Wouldn't that be normal? From more valve overlap on the VTEC profile?

preludesh01201 · 04-06-2006, 03:51 PM

3psi? I drop about a pound at 9spi when in vtec but thats normal.

NoRice4U · 04-06-2006, 04:26 PM

Quote:

Originally Posted by Daemione

Wouldn't that be normal? From more valve overlap on the VTEC profile?

it literally plummets 3psi lower when it should drop only .5-1 psi

sharkcohen · 04-06-2006, 08:04 PM

Is it the Endyn pulley, or the Motorvations pulley?

NoRice4U · 04-06-2006, 08:24 PM

motorvations

sharkcohen · 04-06-2006, 08:41 PM

Yah you should be seeing about 11 psi in the low end and about 9 psi vtec and above. What brand of belts are you using?

NoRice4U · 04-07-2006, 05:03 PM

I don't know what brand the belt is (I bought the kit with a new blower but other components were used). The belt to the blower is very tight and never loses tension; however, the main jrsc belt that goes through the alternator gradually loses tension even after tightening. That is where the problem lies so I'm going to replace that belt this weekend

sharkcohen · 04-07-2006, 07:37 PM

Get Goodyear Gatorback belts for both.

NoRice4U · 04-08-2006, 12:37 AM

Definitely!

Dyno Graph of the tuning session...as stated above, tuner couldn't get rid of the boost drop

http://s54.yousendit.com/d.aspx?id=0...S370D6ZVCEQQ0N

A/F around 12.5

sharkcohen · 04-08-2006, 01:02 AM

sharkcohen · 04-08-2006, 01:03 AM

I would suggest a/f of 11.5:1.

NoRice4U · 04-09-2006, 01:50 AM

My tuner said that at times he would get VERY choppy power curves from my car. As a result he said I could need a 3bar MAP sensor because I'm hitting close to 11psi (limit of stock MAP sensor). Do any 9psi jrsc people upgrade MAP sensors?

Paluce · 04-18-2006, 08:09 AM

nope, no 3bar sensor for me at 9psi.

11.5:1 with a JRSC is perfect. The extra fuel helps cool the air charge. you can run a bit more timing and make more power.

I also use the gatorback belts. They last for ever. I do need to go and tighten the main drive belt every 3 months or so. I also loose boost when the main drive belt starts to slip.

NoRice4U · 04-21-2006, 04:12 PM

problem fixed

new goodyear gatorback belt tightened (both main and blower belts); no more boost loss