Losing Boost??

[gsrev]

Just the other day I noticed that at 7200 rpm my boost guage starts to drop from 7.5 psi (its 50 degrees now) and is reading 5 psi right at redline. What is the deal?? Is it the temperature change?? My car has been running fine but this is just something I noticed, before I never really looked at my guages especially while approching redline. I do not here the belts squeeling like if its slipping. I do know however that my alternator belt is pretty chewed up so it will be replace soon. The actual sc belt is fine and is tight. Hmm??? any thoughts... again it only happens after 7K. Oh by the way, is the alternator belt the same size as stock?? I will do this tomorrow.

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1992 Red Honda Civic CX Hatch Back...soon to be hybrid and boosted
1998 Super Sonic Blue Integra GS-R
Minor bolt ons include:
Jrsc 6psi.. blah.. blah .. blah..
best 1320: 13.783 @101.43 on drag radials

[Holden]

6psi JRSC Belt Sizes
AC ====== 31" === 790mm
PS ====== 36.5" = 930mm
Alt. ==== 31.5" = 800mm
Blower == 24.5" = 620mm

These belts should work unless something is a little different on your setup.

The losing boost thing sounds like a belt problem.

Greg

[00ITR006]

i heard that the boost dropping alittle at high rpms is normal..?? atleast thats what this tuner told me..... I drop from 5psi, to about 4-4.5psi at around 7800-8400K

[Holden]

Maybe it's different with an ITR.

Boost doesn't drop on my GSR at high RPM.

Greg

[00ITR006]

hum, i'm going to have to find out about that, could it be that i'm running extremely rich up there to loose pressure???

[BlownSOL]

I had the same problem until I ran a high-flow exhaust and a set of good headers. VTEC also affects boost pressure drop at high RPM's.

[Mr Rogers]

The way I understand it is that boost will raise in our Vtec range, highest should be at or around redline. Loosing boost sounds like a def. slipping belt and at one point, my belt was slipping so bad due to the badly worn idler pulley, that I saw 5 psi at most Talk about pissed off! I f*cking lost a street race to a damn NOS Nissan 240SX running a 100 shot Good thing I had another guy in the car to say to me as I am getting beat "You aren't biulding boost" and I am thinking to myself "I don't build boost, I have boost now or never". Well I swapped the pulley out as soon as I could and I tell you what, 8psi never felt better But my pride still hurts from that night

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98 GS-scR w/ 8psi JRSC, Walbro HO fuel pump, AEM cai, DC 4-2-1 one peice header, Thermal Exhaust, Skunk Works cam gears, J&S safeguard, RC 310's, Cartech FMU, Vortech regulator, H&R sports and KYB AGX's, and of course to slow down, KVR X-drill F&R rotors and Carbon Kevlar pads and V1 to signal the slowing down and soon to go on the "Juice".

[00ITR006]

Okay so its due to overlap in cams, I knew it had to be something, becaue i loose pressure sometimes a whole 1psi down to 4-4.5psi, Can't really tell any difference in horsepower though, according to dynoes, I would love to hear another SC ITR tell me that there pressure drops alittle at high RPM, then I won't trip as much.. But since my nearest dyno is 2hrs away, I can't visit as often as I would like.

[Marc]

You should not be losing any boost at higher RPMS in a non Type R. If you are that indicates a belt problem. The reason why Type R's will see a loss in boost is due to the overlap in the cams. Cam gears may help prevent this. I know JR Civic was experimenting with this awhile back. I don't know if he ever got any substantial results.

Marc

[gsrev]

Okay.. update. I changed my alternator belt which was majorly chewed up, my sc belt was replace about 10k miles but still looks in perfect shape. I tightned the crap out of both belts. No go I noticed at 8k I am down to 5psi from a normal 7 w/ the 6psi pulley. Granted I don't know how long this has been happening cuz my eyes are always glued to my tach at that high of rpms. I just don't get it. Can it be a sign of a weakening motor? After all I have been sc'd for about 40k miles. But it just wouldn't make sense, I just ran my fastest times this past weekend. I figure I would be getting slower. Another thing that popped in my head.. Could it be the need for valve adjustment or could it be a compression leak? It has been awhile since I got a valve adj, but my valves aren't tapping or anything wierd like that. But then I ask myself if all this were the case, why does it only happen from 7k-8200?? Again.. there is absolutely no audible belt slippage and belts are TIGHT. Arrgh...

------------------
1992 Red Honda Civic CX Hatch Back...soon to be hybrid and boosted
1998 Super Sonic Blue Integra GS-R
Minor bolt ons include:
Jrsc 6psi.. blah.. blah .. blah..
best 1320: 13.783 @101.43 on drag radials