PraxRX7

I need to know exactly the effect of porting a wastegate and what the process generally involves.

What kind of performance does it achieve...what are the set backs and down sides (performance cannot be achieved without sacrifice..)

I am thinking of upgrading the wastegate if I get a better turbo anyways...but just need some actual technical data on actual mods of this kind.

tims

on the stock Mazda second gen turbo the waste gate is part of the exhaust housing. in fact it is a small hole from the turbine side to the outlet of the turbo. controlled by a diaphram and linkage moving a flap over the hole to build boost and removing the flap from the hole to keep the boost pressure at desired levels. this works well with the stock intake and exhaust, but if the exhaust is changed, removing cats, or cat back systems, the boost may creep past the desired level. this is boost creep and it is not controlable and is the number one engine killer for modified turbo II's. the reason the boost creeps up is that the hole in the turbo exhaust housing is not large enough to flow enough exhaust pressure to keep the boost under control. so you can enlarge or port the hole to inprove this or install a seperate waste gate(very difficult). if you are using a different turbo then a new waste gate will be needed anyway as well as a new exhaust manifold.

Dyre

This should help-

http://www.k2rd.com/FC3S/MODS/TURBO/wg.htm

The idea is to get ride of the extra exhuast gases a modified engine produces- The the stock wastegate, it has no where to go, but the exhuast wheel, which spins it faster than your set boost lvl, cause boost spikes---

tims

here is a picture of the new wastegate on my turbo II race car. it is an HKS race gate.

DyNaMiTe KiD

i have a intake and rb turbo back exhaust.. on a 1990 turbo rx7. with stock turbo.. those are the only mods i have. im getting my stock turbo rebuilt.. at what psi do i have to port out the wastegate? my plans are going upto 14 the most.. if i have to port out the wastegate to run 14 psi then i'll wait and stick to 10 psi for now..

thanks..

Scott 89t2

get it ported!! if it's already out why not? it doesn't depend on what boost you are running it depends on how much airflow you have. with the exhaust and intake you are already outflowing the stock wastegate and you will have no way to control the boost. if you are going to rebuild it and want to run 14psi you would be better off getting a bigger compresser wheel and running less.

how did you plan to run 14psi? what other mods?

Scott 89t2

what the hell is that?? that's a weird turbo

Dyre

Looks like someone cut off the internal gate on a stock turbo and weilded a braket for a external gate on it...


Dont ask me why someone would go to the trouble.

DyNaMiTe KiD

Hey Scott89t2

I was planning to run 14 psi with a aftermarket intercooler, msd ignition, apex avc-r and afc also 780 cc injectors and walbro 255 fuel pump..

ontop of that im getting my stock turbo rebuilt, and i will get the wastegate ported, also getting a new factory engine..

am i safe for 14 psi? and believe me thats the most i'll go..if its better off to stay at 10 psi please let me know.. i can wait for a new turbo if ihave to for more power.. a reliable engine is better than a blown one..

thanks...

ps.. whats a bigger compressor wheel? can i put that into the stock rebuilt turbo? or does a bigger compressor mean a bigger turbo??

tims

14 psi is a tough order for the stock turbo especially with a front mount intercooler. the turbo starts to fall off its curve over 10 psi and is better suited to run below that.
As for why I installed the external wastegate, it was necessary to keep the boost from creeping. my car has a nearly straight through exhaust and a straight intake and no amount of wastegate porting could prevent the sudden spike in boost pressure at about 5500 rpm. So instead of a new turbo, intercooler, exhaust manifold, wastegate, BOV, and intercooler piping I decided to add the external wastegate. It was not an easy job and if I had to pay some one to do it for me it would be cost prohibitive. the larger wheel may help your setup and allow you your 14psi boost level. at that level though the stock turbo is working hard to move enough air efficently.

DyNaMiTe KiD

Hey

So i would be safer just keeping my boost at 10 psi right? and its only gonna go to 10 psi when im racing which isnt that often, i only used to go up2 about 9 before neways..

so the verdict is i should stay at 10 the most right.. with those mods and shouldnt have a problem right??

thanks

Turbo FB.

If you install a (pop-it) valve, different than a blow off valve this works off of pressure not vacume put this somehwere on the intake, when ajusted the valve will pop and release charge air to the atmosphere at the ajusted pressure this will save your motor from a massive boost spike. It will however cause a hesitation but
whats a hesitation compared to a blown seal.

DyNaMiTe KiD

Hey

I have a pop off valve already just never installed it.. i guess i will thanks...

DyNaMiTe KiD

hey

i just talked to a guy about porting out wastegates in my area. and he says with the mods i have so far, that i would be losing pressure if i ported out the wastegate.. if porting really isnt a big deal for 10 psi i wont.. cuz around here its hard to find ppl..
any comments/suggestions??

thanks