Think about it, if you have the spring in the bypass valve your always putting that extra load on the engine and blower. Id say more then anything like your AC compressor or alternator combined. Cam and I worked on it one morning testing it, by the end of the day we had a working prototype, I forget whose car it ended up on, I think Roland had it on his for a while. We even tried it on a mustang blower on some guys car that wandered into the shop one day and he even said it worked a lot better.

 

That intake may be part of the problem? 1st of all your air filter is too small for a 6 port motor. I tried that set up and could not get it to work for me. I too had stumbles and my a/f's where not right.
Phil has had MM do a lot of tuning work on his including installing a post blower IAT. If you run a true cold air Intake and the post blower temps are greatly different--then that could also be a problem if you dont do that?
I advise 2 things? 1st check for any small vacuum leaks, 2nd try a different intake with a paper filter like aem's.
Are you running screens? I dont run screens.
You can cut the spring to make it weaker if you want too.
The Pettit metal bypass valve is a really good valve--i have tried others and havent found anything any better.

 

i know there are no leaks anymore.

i'd be happy to try another intake but which air filter would you recommend?

I don't want to cut this spring; just find a lighter one to try.

 

just pick an aem one that will fit your set up--i dont like k&n--i dont think they filter well and they cause more turbulance in the pipe.

 

And the countdown to Saturday Road Racing at Sebring begins...zoom-zoom

 

I always though the boost overcomes the spring to slow the entry into, and out of boost, not the spring closing the bypass at idle and causing boost at idle.

The bypass is held open by the spring, the open bypass allows air back into the intake, this allows for light boost under light load, the added spring makes boost require a longer hold, or harder press of the throttle.

More spring = less boost for the same "foot position"

Is this not correct?

Oh, and the twisty **** on the bypass lets you adjust the pressure "between spring sizes".

 

I always thought also that a spring will allow a smoother transition between boost and vacuum. A spring may help you if you are dying after throttle release?
But if you are dying after throttle release and you were not in boost to start with, then thats a maf problem?
My car does stumble a little at idle when the a/c compressor turns on and off. I hate that but I dont know what to do about it.

 

If you use the spring your supposed to be hooked into the pre blower intake behind the throttlebody. The spring should be able to hold the bypass shut when the vac drops behind the throttlebody. I have the bypass valve locked open for the time being and still see 3 or 4 psi at WOT. Another reason I like not running a spring is it helps smooth out the transition from vac to boost. Also it deffinatly makes for a better crusing when at light throttle.

 

When Bill was working on tunning he was haveing problems getting the idle and low throttle driving to work properly. When we instaled the bypass valve withought a spring it made a world of difference and made everything better.

 

Like I said before you have more load on the engine at idle to overcome the spring. Its more then the AC compressor and altinator at the same time.

 

PRE BLOWER??
Dont understand? Boost will help close it--right?

Juan---you go dude! We were at rd atlanta last w/e and it was HOT! i didnt run--just rode and watched.
Cant wait to see your data findings.

 

guys, the bypass is shut by the spring by default. boost keeps is closed and vac opens it to allow the air to recirc. my issue is that the vac isn't enough to pull the valve open against the strength of the spring. i dont think there's anywhere i can hook it up where that'll work with the stock spring in there.

 

Well, the way its settup on other blowers for other cars, even the ones that come with a blower is you choose the proper spring that shuts the bypass valve without the assistance of boost. We just figured out how to get rid of the spring by plumbing it into the boost vac section of the intake. Hooking it up like that also made it effective also with a spring that's to light to close under boost. The original recommended bypass valve had a butterfly style opening wich dosnt need much of a spring to hold it shut or much vac to hold it open. Not unlike the shuttervalves on our engines.

 

I think if a butterfly style valve could be adapted to our kits somehow(I'm sure it wouldn't be hard) with more volume of bypass it would work a lot better but the cost is more to produce.

 

Ok --got ya.
I am pulling 20 of vac off throttle and i just yesterday cut a spring to fit. I am hooked up post blower and no issues. transitions well. The a/c can cause a little stumble though as mentioned.

 

I run the soft spring of the track to alleviate the hard off throttle transition and no spring while at the track. I clean my MAF sensor before every track event (once a month) using MAF sensor spray cleaner. I run a K&N style air filter with no screen off track and a screen type cone filter with a dirt track sock over it and a MAF tube screen while at the track.

 

Juan --2 days and counting!

heres a couple of our guys at Road Atlanta this past w/e--both of these cars have the LS engine swap going on. They fly and dont break. The are detuned to 340hp to make class

http://garx8club.com/v3/download/file.php?id=3319

 

Meh! I don't have access to the GA website. But don't worry since a rotary car without a rotary engine has no soul. Besides, I rather watch a live vasectomy procedure than a piston engine bay on a rotary car.

 

can you tell me where to buy a softer spring?

 

Lol Juan I hear ya.
We do still have plenty of rotary power out there. One guy is actively racing with a FC turbo car and doing very well agaisnt the crowd. He also is not having any problems. It is track dedicated.

Dondo--just take you spring and cut it--you can streach it to weaken.

 

some nice pics of my new exhaust set up here:

http://www.millteksport.com/product....m?articleid=83

 

Exhaust looks nice! No info on the US Pettit site even though the article says it is available. Did you pick up any power with this exhaust?

 

Nice, cali, hopefully I will be getting this installed at Pettit in August.

 

Rotr8, You getting other work done at Pettit? That is a long way to go for an exhaust install

 

pdxhak, the 1st systems are on the way to Pettit US, and should get there mid July.
Should do well powerwise, as we measured a fair bit of back pressure with the OEM system and this flows tons better.