Greddy Kit Making Too Much Boost!
 

Recently put on a turbo tony downpipe and the car makes 5psi for the most part and makes 7psi the last 1500 to 2000 rpm. Anyone else see this with there car? Just after the downpipe I changed the wategate actuator to a better garrett unit from FM and never set the arm up perfect so it only makes 4psi and still makes 7psi up top. UEGO still reads good for a/f ratio so not sweating it but was curious.

There is no such thing as too much boost. The answer is ALWAYS more boost.


PS. I dont have an answer for you.
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Maybe you have reallllllllllllllllllllllly late spool

ThePass is right, the greedy turbo is huge and is famous for spoiling late

Or maybe that large exhausts are notorious for flowing well and can often overload a small internal wastegate?

maybe something like this:

Attachment 207527

Isn't this called boost creep?

Stock greddy wastegate did this and same thing with this bigger better unit (Flyin' Miata : Turbochargers : Parts and upgrades : Adjustable wastegate actuator). I have a manual boost controller that I handn't put on yet but I doubt that would do anything other than allow me to up the boost back to 5psi and then it will problaly spike 8psi or so. Just seems odd any other turboed cars seem to have the opposite problem; spike low and leak down up top.

Seems that I've read on multiple occasions that this condition is due to sourcing the boost signal from the hotside.

And the problem you are experiencing is often related to a combination of a small turbine and a small wastegate opening, as alluded to above.

unless your making over 15-16 psi your not running enough boost with that turbo

I have the tony dp on my greddy set up. I see the same thing. I left the waste gate a little loose so it would hold around 5-5.5 psi. But in a 4th gear pull on the freeway it will creep up to 6psi at the top of the rpms. Not quite as much as you are seeing.

I think this is your answer. :bigtu:

If I were you I would get a MBC - even if you want to run only 5 psi, that will do a better job of holding it at 5 than the wastegate alone. The greddy wastegate gets a bad rap but I've found recently that most of the problems people have with it is either a.) people aren't using a tried and true (and affordable) MBC and b.) they have the wastegate signal coming from the hot side (compressor nipple).
Many have swapped the greddy wastegate out for a "stronger" replacement and not accomplished any difference other than being out $100+.

Please tell us what the rest of your exhaust is like. To be honest, the greddy turbo is larger than a lot of the garret units many are running on these cars. Most people slap a BEGI kit on and immediately get nice spool but for the greddy crew we have to work and tweak things to get that spool down.. with a free flowing n/a exhaust my stock greddy kit was not getting 6 psi until 4700 rpm - that's 2300 from redline, not much more than you are saying. Until then it would act just like you say yours does: it would hold a few psi and then surge up to the 6-ish once I hit the rpm it could spool fully at.
Now, with a BEGI divorced gas downpipe going to a 2.5"->3" expander and then a 3" cat, 3" resonator and then a turn down at the rear axle, plus using MS to tune in more spark advance and a bit leaner a/f ratio in the lower cells to spool the turbo fasterI get 6-7 psi by 3500 and 12 psi by 4250. Much better, still not nearly as soon as the guys like Sav who can get 12 psi by like 3k but then again, he had to spin up to 16 psi to get 230 whp and was at the top of his efficiency range and with our turbos we can get 230 with 12-ish psi and efficiency is great up to 275 whp or so... it's a vicous give and take sort o deal ya know..
So.. what's your exhaust?

Exhaust: https://www.miataturbo.net/forum/t31526/

HEY dan leave me feedback thanks man...:).............. sorry to thread jack!

This happened to my set up over the weekend just gone and, like you, it was after fitting a 2.5" downpipe. My EBC managed to hold target boost (8psi) upto 6k rpm, then for some reason the boost increased or crept upto 9.3 psi at 7.2krpm. My Link map limit was set to 165kpa otherwise I'm sure boost would have exceeded this figure.

Know idea why

:dunno:

Again, too much exhaust for little bitty wastegate hole.

You open hole now, ok. Add larger flapper, too. Shrimp fried rice $3.99.

People have them ported all the time to stop the creep. Or just expect it to creep due to an inadequate wastegate.

Corky Bell, in his book, said that sometimes two wastegates are necessary or even desirable to relieve excess pressure effectively. But it is cheaper and easier just to enlarge yours.

BTW - Adding a better flowing exhaust doesn't create the problem. It simply exposes a preexisting deficiency. The large delta between the inlet and outlet of the turbine created by the better exhaust is highly a highly coveted situation and means increased efficiency and reduced losses.

You have reached a point where you have found a limiting factor, just like the transmission and diff are only good for so much. Or the intake manifold's flow capacity on the thread about dyno #'s just posted yesterday. There are design limits to every component.

I'll have to add another wastegate IN the exhuast like a C6 Z06...lol
http://www.southerncarparts.com/imag...on-exhaust.jpg

If the wastegate flapper for the TD04H-15G is too small and therefore adding a larger exhaust causes boost creap, why then does my 2.5" BEGI Divorced gas DP -> 2.5" to 3" expander -> 3"cat -> 3" glasspack resonator -> turndown at axle hold 10psi from 4k to redline with no creep? Except for the cat my setup is basically a resonated dump pipe like a race car. I have not changed the wastegate nor done anything else that would effect it except use a simple cheap MBC.

Your running more boost. Most likely if you tried to run only 5psi you would creep some.

Thanks for that.

The Link ecu has a way of eliminating boost creep, so I'll have to make the appropriate adjustments. I'll call FM later to get some suggestions for waste gate loop gain settings for the Greddy.

You beat me to it.