ghostsi

Ok guys went and got the car tuned by dave today. We hit the streets with a GM 2 bar (thanks to 88dx). Dave got the car running good but we have a small problem. I have the greddy spec b boost controller and we were messing with it but can't seem to get the damn thing to hold boost. We would get it to spike to about 15psi then drop down to 11psi We went back and installed a MBC and it really did not make a huge difference.


My question is PORTING the internal gate. Will this make a difference in holding boost. Also how easy is this? I tried searching HT and came up with this

[qoute]With low load, your RPMs will be rising quickly and the massflow the turbo has to put out increases quicker at the same pressure. Look at the speed lines on a compressor map and you'll see that when you run the **** out of a small turbo(like you are doing), the compressor can slowly accelerate in the low/midrange, then as you start running the poor bastard off the edge of the map the speed has to increase really rapidly to keep the pressure up for the massflow the engine is wanting to consume at that pressure ratio and RPM. In 2nd gear your engine is accelerating so quickly that the turbo just can't physically accelerate the compressor wheel fast enough to keep the pressure up.

It's actually pretty common on small turbos, you just don't hear about it on these boards much because everybody thinks a compressor the size of a small child is "moderate." hah[/qoute]

Jeff what would you charge to make me a log mani dumptube and downpipe? new turbo time maybe

LateApex

The problem is the wastegate being blown open by high exhaust manifold pressure. Porting the wastegate hole will actually give the gas more surface area to push against and make the problem worse. Get a Forge Motorsport actuator or add a small spring between the wastegate bracket and flapper arm and do port the wastegate hole, it is way ------- tiny on those Greddy snails.

boosted_b16

the greddy elec. controller is garbage to start with, ---- that expencive bull ---- it never works right, stick with a mbc, and second just hook it up with an external wastegate and ---- all the other crap.....

SpankedYA!

Wrong, its a good unit if you know how to set the gain versus increase. Drop the gain to between 1-3 and then increase the percentage setting from there. The gain setting removes the spike. The increase comes from the main percentage setting, not the gain setting. My internal gate turbo did that till I adjusted the EBC correctly.

HMT-Admin

Not always, If the gate is being forced open by exhaust pressure there isnt much the boost controller can do.

Internal gates suck *** over 12psi anyways they never hold steady. Donavan I would make you a manifold however I'm going to be pretty busy the next few months. Plus I'm not a big fan of PS/AC

Why not just blow a hole in your greddy mani and put a external gate on that bitch.

ghostsi

i could jeff i am kinda cut off of spending money right now anyways. The car runs good and steady at 10lbs i can live with the spiking for a bit. I think the car is getting parked for the winter anyways. I may be in contact if you want to make me a new mani in the spring summer time. But i would need to find a new turbo as well. I can put all that stuff on myself I just do not think i could build the block myself.

leed

I ran his EBC w/ the gain all the way down and all the way up. W/ it down, the boost tapered to about 12psi instead of the 10-11. This is with the other boost **** cranked all the way up. hahaha
I put on the MBC and got the exact same results.

Poor Donovan, his overweight SI feels like it got a LS swap or something. Wham....Boost/TQ hits, then it ***** itself at 7k. By spring time, Im sure you'll be able to muscle some money outa the wifey.