Boost problem

[MarxMcrae]

Hi guys any help with this would be welcome
Got a 93 FD with stock twins and if I accelerate hard through a gear past 5/6k rpm and then change into the next gear there is no boost, then when I let off the accelarator it makes a wooooing noise (no its not the dump valve making the noise)
I really have no idea what the problem is. I've got an Apexi D/valve on which i thought could be causing the problem, but im honestly at a loss

Marx

[McCARTHY]

i would say get it checked out by a spcailist just to make sue everything is ok.

[Bobfish]

does boost build very slowly after transition? Eg if you boot it past 4.5k rpm and then change, will boost build very slowly in the next gear?

If so, problems like this are often your turbo control solenoid - its located under the UIM and basically normal operation is that the turbos pressure the pressure chamber, and the turbo control solenoid keeps the secondary turbo actuator from operating, meaning you only work on one turbo. At transition, this solenoid opens, allowing the boost from the pressure tank to get to the actuator and bring the second turbo online. With a bad solenoid, the springs inside that close the valve get tired and cannot shut the solenoid after it opens due to the boost in the pressure tank. This means that both turbos are being spun up at once causing VERY slow boost build.

PM me if you want; i know a bit about the turbo control systems and do private work. See www.face2faces.co.uk/RX7 for a few examples of my work (see the how to section)

[MarxMcrae]

Cheers Bob, it does sound like a similar problem. If this is the problem is it gonna be best just to get a now solenoid??

[MarxMcrae]

Oh by the way nice website, very informative!

[Bobfish]

yes it will be a new solenoid. I suggest you (if you have the ability) pull your upper inlet manifold and solenoid rack, replace all the lines, and vac test all of your solenoids. I you need help doing this then i can provide phone support, or if you want to drop the car down to me for a week or so i can do the job for £300 + parts (i will fully guarentee a perfect boost pattern after the work)

[Bobfish]

by the way, i would estimate that its about 8-10 hours labour to do the solenoid rack properly (i.e ALL lines, not just the ones accessible with the UIM Removed) so you think 8x£40 an hour labour + VAT is £376. Im pretty cheap considering the work's guarenteed!

[Martiny]

Marx do you have a boost gauge? My suggestion is first install one, then post back here the exact boost pattern you have.

it should be about 10 PSi up to 4.5K , then a quick dip down to 8 Psi and back up to 10, maybe dropping to 9 when you get to the red line.

We usually post it like this, "My boost pattern is :10-8-10", ( or whatever)

[Bobfish]

yes thats very important, but ive experienced the same problem myself - my car is doing the same as his at the moment, havent had chance to replace the solenoid yet though. Cars coming off the road for the winter for an engine rebuild so ill do it then.

the problem is hard to pinpoint, its an odd boost pattern, basically you get perfect boost from 2k up to redline, but if you drop down below 4.5k but not below 3k, when you floor it again, you get very slow boost build to 10psi and no transition (because both turbos are being spun up)

[Glenn Butcher]

Hi BobFish,

I know you are trying to help a fellow rotary owner out here (which we appreciate), but you are acting as a Vendor on the site. We will let this one go, but if you want to keep advertising your services you will have to become a Trader.

Regards,
Glenn

[Bobfish]

sorry mate, didnt know that was a rule :( Ill stop it in future!

[Glenn Butcher]

No stress at all! thought we had better mention now before our Supporting Vendors jump on this.

[MarxMcrae]

Yeah i do have a boost gauge and to be honest it goes a little something like this...
Up to about 12psi then drops right down, then back up to about 8psi if that, but i'll take the car out later and check