greddy wastegate woes
 

so, i've just spent some time looking around for some definitive info about the greddy wastegate issue i'm having (which seems common) of being able to make 12psi at like 4k, but losing 3 - 4 psi between 5 and 7k.

i know there was a lot of speculation about this, and a few of you bought replacements etc... but i wasn't finding any posts where anyone actually replaced it with something else and said "hey, that worked!"

did i just miss that, or has nobody actually remedied the problem with a different actuator? i know Ben was able to sidestep the problem with EBC, if i remember correctly, but right now I'm limited to manual boost control until i get around to modding my MS for EBC.

I know of two people who simply got new actuators, adjusted the arm length, fabbed up brackets, and rocked out. Kotomile might have some pictures of his posted under his recent dyno thread. Joe Perez might have pics somewhere too, he's generally pretty thorough.

Even with the EBC maxed out, I still loose boost up to redline. But I'm also starting to wonder if it's due to not just the crappy actuator, but also due to insufficient compressor.

it's probably a combination of factors. but the wastegate actuator is notoriously shitty, so i was looking to see what kind of reward i get for my effort. i feel like at least partially solving my "boost till redline" issue would snag me an extra mph or two in the traps, and generally make the car faster and more fun.

It's definitely going to be a worthwhile thing to do. I've got a 16G actuator that I'm going to section and shorten the arm (with a turnbuckle for adj length) and weld up a new bracket to once I have a free weekend. It'll be a few weeks at least.

I think i remember somebody using a 300zx wastegate

This issue frustrates me too. Always a 1-2 psi loss before redline. We've got to come up with a good affordable solution for this..
EBC is great, but doesn't really address the problem.. if the problem is that the actuator is weak, we need to find an actuator that has a good adjustability range for our cars, and find an easy way to swap it over.

yeah rappadan did this. his holds strong to redline.

THATs who it was. i knew i remembered someone dicking with something like that... guess i didn't pound that search button hard enough. :-P

here fool: https://www.miataturbo.net/forum/sho...ight=wastegate

bitch! i will teabag your Ralph Macchio looking ass before you know what hit you.

something interesting i took away from revisiting that thread, though, was why more of us aren't changing the location of the boost reference away from the compressor outlet and to a post-IC pre-TB location.

brain, you quoted corky's stuff about boost signal locations and the only argument against going to a post-IC signal was a potential temporary heat blast to the IC at boost onset. without trying it, i guess i won't know for sure what the tradeoffs really are, but having a signal much closer to the TB, after a flow-dependant restriction in the piping (intercooler) makes a lot more sense.

The insane boost dropoff we see with the typical installation is probably a combination effect of the craptastic greddy can and the increased pressure drop across the IC at higher boost and rpm levels.

guess i will know better once i move that signal line and make some runs to test it out...

You might want to move the signal line to post intercooler, but also put a check valve in line. the check valve would not only eliminate vac on the diaphram, but should also smooth out the signal.

hmm, probably won't hurt. but really think i'd see measurable vac before the tb?

no, i was thinking from the manifold, especially near the rear where the signal will have the least oscillation

i'm thinking about essentially where Abe put his. this way as the flow across the IC increases (which will magnify the effect of pressure drop), it'll be accounted for in the signal that makes its way to the wastegate.

between that and a helper spring, i am thinking i might be able to cut boost drop down significantly. worst case, i replace the actuator anyway.

maybe if i have a bit of time this weekend i'll pop off one of those sections of pipe and install a vac signal source, and will have some direct comparisons.

I was actually wondering about EBC and boost loss. So even with the EBC the boost drops? Looks like I'll be searching for a new can. Stupid greddy crap.

the EBC can help remove it, as it will be able to close the wastegate as the rpms increase, negating the effects. However, I think Ben goes to 100% close line at redline...the actuator itself just stinks.

Yeah, IIRC Ben was/is running 100% DC to redline just to maintain maybe 12-13 psi (correct me if I'm wrong Ben). My DCs don't leave the 50s and it will hold 15 psi to redline, the Greddy actuator is crap!

I bought one of these: http://flyinmiata.com/index.php?dept...umber=02-70570 used from a member, you'll also need the rod end for it http://flyinmiata.com/index.php?dept...umber=02-70571 . The thread is 1/4" x 28, which I found was impossible to locate in my town. ATP sells a WG arm extension kit for $8 (with $12 shipping..) to lengthen the arm, which you'll need unless you have other means of lengthening the arm to reach the Greddy's flapper. It is a strong can and will hold whatever you desire boost-wise to redline. After scoring those all you'd need is to make a bracket out of flatstock to mount it up.

Attachment 213051
Attachment 213052

Lmfao meatwad ftmfw!

I too am dealing with the Greddy gate woes :vash: I have a had no luck stabilizing the boost with the EBC and went back to a MBC to make sure the EBC was working right. I see a different problem from you guys, when I get in to it it hits 14-15psi than drops off to 11psi ish and then rises back up as the RPM's increase to redline. It gets back to 14 PSI by red line. Is this still the WG?

I have a helper spring on it right now.

i think it's still the wastegate, mine did the same thing on the dyno, now i think the helper spring is fatigued since now it's not rising back up anymore. this is going to be a project for me as well. anyone have any luck with the cheaper ebay wastegates?

I have a brand new 8psi wastegate can. This is the same one that Joe used on his greddy kit.

http://www.flyinmiata.com/index.php?...umber=02-70576

$35 + shipping.

Whats the diameter on the can? There not much room there between turbo and valve cover. If it fits I'll take it. PM me your paypal info.

This is the same unit that Joe Perez used on his Greddy kit, so I assume it'll fit. I bought it originally to use with my Greddy kist, but I went with a different turbo setup and don't need it any longer.

I won't be able to give you a shipping quote until tuesday, tomorrow is a holiday here.

Jay

Took me a while to find the pictures. My bracket actually isn't as cool as Koto's, just a piece of 16ga sheet steel. Also, mine is a different can; rather than the two studs, it has a welded-on flange. Otherwise identical, but I got it new on a DOTD quite cheaply.

The bracket on the WG can had to be trimmed significantly. You can see below how the position of the nipple relative to the bracket is wildly different. Thus, the new one is rotated appx 90° CCW (viewed from front) relative to the old, necessitating the trimming of its welded-on bracket.

I also cut the rod and eliminated the latter of the two bends, causing the end of the rod to be offset relative to centerline. The rod was almost exactly the correct diameter for threading to 1/4-20, so I just ran a die down the ends after cutting, and used .25" threaded hex couplers to re-assemble. (when threading, support the rod in the vise, not the can)

The two together, before modding the new one:

http://img265.imageshack.us/img265/8...ebysidegw6.jpg


The new can in place, modification of rod is obvious:

http://img164.imageshack.us/img164/9872/topviewgq4.jpg



Slightly better shot of bracket (this turned out to be hard to get a good picture of):

http://img91.imageshack.us/img91/3662/frontviewrx8.jpg


The holes in the compressor that the bracket now is fastened to were filled with setscrews originally. Just pulled 'em out and replaced with bolts.

No helper springs, and with the MBC she holds a rock-solid 13PSI to redline.

Thanks Joe. If this works great....if not I'm welding a external WG to the manifold and I'll be done with this once and for all.

One small epitaph- I did this because I too was having problems with boost dropping off with RPM. If it was at 13PSI @ 3.5k, it would gradually drop and by redline be at maybe 10PSI. This can did not (by itself, anyway) solve the problem.

AbeFM gave me the answer, which in retrospect seems blindingly obvious but at the time hadn't occurred to me. I was still taking the WG boost signal from the stock location on the compressor- before the intercooler.

The intercooler is a restriction. Thus, when air is flowing through it there is a pressure drop between the inlet and the outlet. The amount of this drop is not a constant- it rises proportional to the volume of air passing through the intercooler per unit time. More airflow, more pressure drop.

So what was happening is that the WG was indeed holding a constant pressure in the system before the intercooler, since that's where its reference signal was. After the intercooler, the pressure dropped with RPM because airflow obviously increases with RPM. As the RPM climbed and the mass of air passing through the I/C increased, the pressure drop across he I/C increased and this was reflected in my MAP gauge.

Installing the larger can helped somewhat, and it's obviously a beefier unit- it was not cost-burdensome and I'm glad I put it in. But installing a nipple in the pipe between the I/C and the TB and feeding that into the MBC and WG was what really made the boost rock-solid.

Coming from you, sir, that means a lot!

I'm going to have my bungs welded on my TB pipe soon, is this something you highly suggest? What did you use as a nipple?

:rly:

would you recommend doing this even with EBC?

With MS and an EBC, you would be getting your signal post intercoller. The EBC will be working off the MAP sensor for MS, and I don't think any one is hooking there MAP up to there turbo housing.

'cept the way a lot of us do it, the MS isn't basing its EBC table off of the MAP sensor, it goes off of the duty cycle targets table, which doesn't read any sensor.

I have a funky idea! Forgetting about the wastegate flapper, how big could you port the wastage hole on the greddy turbo? Might be an option to run an external wastgate, but using that hole to feed it.

That just sounds obscene...

I used a 1/8"NPT to 3/16" brass hose barb fitting from ACE Hardware. Drilled and tapped a 1/8"NPT hole in one of my pipes and just threaded it in.


Right.

I mean, either way to can tweak it in software- if it's closed loop than the MS will handle it, if it's raw DC then you'll just have to scale the numbers down a bit towards the top. But I think it'd be easier to do with the drive air from a post-IC location, so that there's a linearer relationship between it and actual MAP.

(Is linearer a word? More Linear. Linearer. Yeah, I like it.)

I got a free can off a turbo from a VW 1.8t. I'm gonna cut the bracket and weld and rig it the best I can to get it to fit. I have no idea if the threads are going to mate up but we'll see. Worst case scenario it'll fail to open and I'll blow the motor.