Does anyone have any idea why I only get 5 psi with a 8 psi pulley...my mods are.....

RT cats
350evo TB
Crawford Headers
Nismo Exhaust
TS L-spec

 

Most likely your belt is slipping. If you can twist the belt 170 degress with your fingers you need to tighten it up.

 

Belt slip is possible... maybe you have a boost leak...?

 

just tightened the belt and going to test drive.....how accurate is the boost guage...?...its an autometer

 

Whats should the A/F be reading at full load....It reads in the low 11's...? will the R4 software help...?

 

Boost gauge should be fairly accurate. Is your A/F gauge wideband or narrowband? It should be 12.5-12.7 when WOT for FI. Also, another thing I thought of is; you won't see 8lbs of boost with an 8lb pulley because of the other mods you have allowing the air to exit the engine faster, so it doesn't build as much pressure on the intake side of the engine.

 

12.5 is too high at WOT. 11.5 is the target.

--Steve

 

I have heard this before, is this proven??? The valves in your engine should keep the boost built, since you cannot force air out of your engine, IMO. I have a 9lb pulley and regularly see 9.5psi at 6800 rpm. I have a Stillen X pipe sedan exhaust and crawford cats. Also have the crawford plenum.

 

will a 9 psi pulley help?.....my other question is the noise coming through the firewall at idle...it reminds me of the sound the impeller in my jet ski makes....

 

My car is proof that that an exhaust that is to free flowing will not build boost . I had headers, RT cats, stillen true dual , Crawford plenum . I could only get 7lb,s boost and 7.6 with the 3.125 pulley. I now have the Crawford cats . I noticed my A/F was outta wack so I did some recorded runs with the SS box , and R4 software . I did several runs thru 1st and 2nd {streets] and I got 8.9lb's at 6,800 rpms. So if you have an exhaust like mine was, you will have trouble building boost .It seems like this engine needs some back preasure some where . I know the RT cat are much loader than the Crawford cats . But from the flow charts I seen are not that much more restrictive. Doesnt it cost alot of money to learn about this motor....lol....yes it does...lol........Bill

 

would stock cats help the back pressure?

 

I have NISMO headers and Ultimate Racing Cats - Frankly I'm hoping that boost comes in at 7lbs with the Vortech kit....this can only help with reliability right? albeit it costs 30-50hp

 

The stock cat will make back preasure ....to much

 

here is the graph

 

I'd almost be willing to bet that your autometer gauge is the culprit. Those things are notoriously inaccurate. Two of my friends installed them on their TT's and they only showed like 4psi of boost..instead of 5.5.