So I’m having a problem with boost spike. I just replaced all my wastegate and controller lines with 1/4” vacuum line because I had a mixture of all different sizes and some pieces where also a lot longer then they needed to be. Unfortunately that didn’t work so now I guess it’s time to move to the wastegate.

I have an on3 kit on a 92 fox with a 7675 precision turbo. I know the wastegate location on these kits it less then ideal but the way it’s configured options are limited to where one can be put. Right now I have a turbo smart 45mm gate on there and I guess because the location it just can’t keep up. Has anyone had this issue with this kit? Did you guys move the gate or add one?

I know ultimately you want the gate where both primaries meet but there just is no space on this kit.
In this pic you can see it basically just bleeds the driver side.

would just installing a bigger gate maybe do it?

anyone that has had this issue your input is appreciated

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Are you a member on Corral.net?
I haven't seen you post this question there and there are a good many people on that forum that run the ON3 stuff. Maybe someone has moved it that can give some good info.

ks

 

I am a member of corral someone mentioned moving it but it still only took care of the drivers side not both. I would just like to see if anyone else did this without any other problems before I do it

 

Something that may give you an idea is that the tube to the WG doesn't have to be a straight pipe. It can be a sweeping bend to get the gate into a better position. The critical part is the angle that the tube connects to the main piping. The flow from the pipes should flow easily into the tube when the gate opens.

ks

 

Boost spike as in it gains a couple psi at the shift and levels back out or just keeps gaining boost uncontrollably?

 

When the boost comes on it comes on quick and jumps to 18-19. The tuner has it set to run 16. Before he lowered the boost cut he said the boost would come on hit 19ish then come back down to 15-16. I think the boost cut is set at 18 right now so when I get traction and build the boost quick I just hit the cut and let off so I don’t know what would go on after that on the street.
The tuner told me though that he would get a spike then it would level out to where he wanted it

it’s not during the shifts just after when the boost starts to build again

I really only hit it in 4th gear because there is no traction in any other gear. Even 4th spins sometimes but when it gets traction and loads the turbo is when the spike hits

 

That might be just a little stickiness in the gate. Usually when a gate is too small or out of priority you will see boost creep, where the boost just keeps building. Pop the gate off, disassemble, clean, deburr, lube with anti-seize, reassemble. See if its better, this is fairly common practice with knock off gates.

 

yeh it sounds like the gate is doing its job. Just a bit slow.

 

X3, sounds like the opposite of creep. Boost controller of some sort? Have you verified that it's not a controller issue? If it's a ball and spring mbc that could be an issue.

 

It’s one of the Mac electronic boost controllers. And the wastegate is a turbo smart 45mm I got rid of the on3 one. I can still take it off and see what I can do with it. Like I said I am going by what he told me that it’s spiking then leveling off. I can’t see it because I hit boost cut and can’t stay in it. I was thinking also to maybe get a bigger gate and put it in that location but idk if it will work because it’s a bad location

 

Try improving the location first, that will helpa bunch.

 

I personally would test more before changing it. If it were creeping, I'd say absolutely, but I would want more info before changing it up or throwing parts at it. With the boost level you're at, location becomes less important. Bypass the controller and test.

 

Location wise I feel I’m kinda limited there is really no room up where the 2 banks meet. I been searching around and it looks like I found another guy with the same kit and he just put his right before the 90 on the crossover and was able to have it work that way. Still just bleeding one bank though

 

To test it on spring pressure what would I do just pull the vacuum lines off the gate?

 

Reference the lower port to your boost source (preferably the compressor housing).

 

I just realized you have the wastegate on one bank. I couple local guys to me have done this in the past only to have weird boost control issues. They made changes and all was good. Having seen the issue with them I have never set up a hot side like this. Ive never once had an issue with boost control or even boost spikes at the shift. That passanger bank is probably venting back into the crossover.

If you had the two banks divided and an split scroll turbine you wouldnt be able to control boost at all.

 

Do you know the changes those guys made to make it work?

 

Cool, thanks I’ll give it a try

here is a picture of what it looked like when he ran it on just the Gate but this was early on in his tuning process he said once he started using the controller he was able to make it level out. This was a run to 6,300 and I have a 7lb spring. This was definitely boost creep right?

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Yes, that looks like creep, but there could be other factors other than just the gate causing it as well. Retarded ign timing can cause creep, and creep is more of an issue when trying to run low boost. A good tuner can do a lot with an electronic controller. It may still creep on spring only, but if it gets rid of the spike, then I think you can rule out the gate as the issue, and look more towards controller tuning.

 

Yes he said the timing was way low there. I’ll give a shot on just spring and see what happens