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Old 04-07-2008, 11:26 PM   #1
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Default First boosted autox - many growing pains

After autocrossing this red race rat for 2 years on big grip and light weight alone, yesterday was the first time I brought it to the cone zone with a turbo on it. Setup as of now is a Greddy kit, adjusted to hit 4.5 psi (it was doing ~2.5 psi when I put it on) with a DIY intercooler - 12x18x3 core the same one Brain is using. BOV has not gone on yet. No MBC. Timing at 5* to be safe until I megasquirt.
Power up top in the rpm range was decent, but anywhere under 4k rpms it sputtered and trudged along and I had to sit and wait for it to hit 4k to begin to pull. I assume this is the problem that many fix with the o2 clamp? I'm thinking that the combination of the stock ecu leaning it out under 4k and the timing being down at the south pole at 5* that those were the cause of the complete lack of bottom end. Thoughts?
Also, in third gear the boost will pick up to a solid 4.5 and then just before redline it drops down to 3.5ish. But in second gear, it spools up to 4.5 around 4k and then by 5k it immediately begins to drop again, and gets all the way down to 2.5 psi by redline. Since I spend most of an autox in 2nd gear this is the most important area to be in boost... Is there a reason it drops off like that? Shoddy wastegate? What can I do to get it to hold boost to redline? I've heard a mbc helps with spool, but would it help with this issue? Should I be looking at a different wastegate - I've heard mention of the 300zx wastegate working on the TD04H is this true/a good idea for me?

Current plans are to add megasquirt with 400-something cc injectors and tune at 8 psi. Timing and fuel will be adjustable then. Also, will get my greddy knock-off bov adapter welded on and install that (recirculating) and will remove MAF. I think that should result in the car pulling much harder in the low end coming out of corners, and I'm hoping for it to hold boost through the powerband instead of tapering off.

Any thoughts?

-Ryan
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Old 04-07-2008, 11:42 PM   #2
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MS with EBC and you'll likely be fine. I wouldn't mess with your current setup, just get to run it and go from there.
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Old 04-07-2008, 11:55 PM   #3
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at 4.5 psi and 5 degrees timeing, your car must be slow as hell. Bump it up to 8 degrees and 6 psi boost.
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Old 04-08-2008, 12:57 AM   #4
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Two reasons I have not bumped it up to 6 psi yet:
Still using the Vortech FMU - so adding another pound and a half of boost would be upping the fuel pressure 18 psi, and it's already maxing the stock fuel pump.
Also, my wastegate must be weird because I adjusted it down almost to the max you can adjust it, AND put a 1/8" washer between the wastegate bracket and the turbine housing to pull it even farther back and now it's just barely hitting 4.5 psi. I literally don't think I can get it up to 6 psi with this wastegate without a MBC.
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Old 04-08-2008, 01:11 AM   #5
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Quote:
Originally Posted by ThePass View Post
Two reasons I have not bumped it up to 6 psi yet:
Still using the Vortech FMU - so adding another pound and a half of boost would be upping the fuel pressure 18 psi, and it's already maxing the stock fuel pump.
Also, my wastegate must be weird because I adjusted it down almost to the max you can adjust it, AND put a 1/8" washer between the wastegate bracket and the turbine housing to pull it even farther back and now it's just barely hitting 4.5 psi. I literally don't think I can get it up to 6 psi with this wastegate without a MBC.
Maybe an exhaust leak? I had an exhaust leak between the turbo and the manifold and I had trouble making boost and spool was slow as ****.

Smart to be cautious.
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Old 04-08-2008, 01:14 AM   #6
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Quote:
Originally Posted by ThePass View Post
AND put a 1/8" washer between the wastegate bracket and the turbine housing to pull it even farther back and now it's just barely hitting 4.5 psi. I literally don't think I can get it up to 6 psi with this wastegate without a MBC.
wait, i dont understand that statement. your wastegate actuator is attached to the turbine housing? Do you mean compressor housing? Also, how would putting a washer there increase boost? Maybe i am totally confused and misunderstanding you.
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Old 04-08-2008, 02:49 AM   #7
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Yeah man, not even 5 psi and only 6 deg of timing is pretty damn weak. I would at least bump of the timing to 8 until you get a megasquirt. Also +1 on megasquirt and ebc, should solve all your problems right there.
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Old 04-08-2008, 03:07 AM   #8
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yeahhh mannn you should totally bump ur timing and increase boost cuz it'll b fasterzzzz, **** motor safety mannn

Ryan, you should be able to do more than 2.5psi. You may as well change the wastegate actuator now; I have heard that makes a huge difference. Your intercooler setup is sweet, BTW.
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Old 04-08-2008, 03:08 AM   #9
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Bump up your timing or you'll start melting ****. It will also help with your low end. You should also think about adding a decent downpipe and exhaust.
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Old 04-08-2008, 03:21 AM   #10
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Whatever you do, just listen for knock and watch your OPG. Twitching under load means knock.... Its like knock knock, who's there, predetonation... ****.
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Old 04-08-2008, 03:34 AM   #11
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Post pics of the IC setup.
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Old 04-08-2008, 06:58 AM   #12
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Quote:
wait, i dont understand that statement. your wastegate actuator is attached to the turbine housing? Do you mean compressor housing? Also, how would putting a washer there increase boost? Maybe i am totally confused and misunderstanding you.
Sorry, yea the compressor housing. The washer pulls the wastegate actuator and rod farther away from the wastegate... the previous owner already had a small washer in between there and when I took it out to see what would happen I was getting 1 psi less. Since the rod is almost completely tightened down, I just put more/bigger washers in between the wastegate actuator bracket and compressor housing and now I'm "up" to 4.5 psi... just seems reallllly odd to me when some are saying they can adjust to 6+ psi with this actuator and they aren't even using washers at all.

Quote:
Bump up your timing or you'll start melting ****.
huh?

Quote:
Post pics of the IC setup.
Will do tomorrow.

About the actuator: can't find more than unhelpful mentions of upgrading the greddy actuator with the search function. Anyone have a link to info on a better actuator to throw on this thing?

-Ryan
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Old 04-08-2008, 07:15 AM   #13
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I am mostly impressed that you where able to monitor the boost at what rpm during an autocross run. One eye on the road?

BenR is referring to the increased heat in the exhaust system that retarded timing causes. Is your manifold glowing like Rudolfs nose?
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Old 04-08-2008, 08:00 AM   #14
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Check all your clamps. I had the same problem. I was getting low boost like 4psi even with the rod tightened so I checked all my clamps and one of them wasn't that tight. After i tightened it. I was boosting 6psi. If it makes you fell any better im running Greddy with IC at 6psi and timing of 9* and there no knock at all. Stock injectors and vortech but except I have a MBC and a BOV. But im telling you if you bump your timing from 5 to even 8 you will get alot of your low end back.
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Old 04-08-2008, 08:21 AM   #15
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the lower the timeing, the higher you EGT's, thats why Ben said you were going to melt ****.

Im running 10 psi with 10 degrees timeing, a vortec, and 305cc injectors. You can bump up the timeing with no knock.

Its ok to max out the fuel pump, ive been doing it for a long while, about 75ish psi it where it maxes out.
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Old 04-08-2008, 11:33 AM   #16
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This is the main thread I know of for the greddy actuator upgrade, atleast it's the biggest one I know of.
https://www.miataturbo.net/forum/sho...eddy+wastegate
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Old 04-08-2008, 01:08 PM   #17
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i have the greddy kit, after installing a full exhaust, i mean downpipe and all, it spools fully at about 2600-2800rpm
im at base 5 degrees too, i dont want to blow anything up, but with the wastegate tightened, i get 6psi

get a full exhaust, and you will def see some gains.
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Old 04-08-2008, 01:37 PM   #18
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ohhh, the wastegate actuator bracket is attached to the front of the compressor housing... it all comes together. Mine is attached to the back so, putting a washer in there would give me less boost.
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Old 04-08-2008, 08:46 PM   #19
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Ohhh never thought about the heat that would be generated from retarded timing! Thanks for the heads up.

I posted the pics of the intercooler:

https://www.miataturbo.net/forum/sho...183#post240183

And, here is a picture of my washer ghettoness with the wastegate actuator:

You can see the washers between the compressor housing and bracket, and you can also see that i have almost no threads left to tighten the rod down any more....
Maybe I have a loose hose somewhere...
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Old 04-08-2008, 10:05 PM   #20
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Quote:
Originally Posted by cjernigan View Post
This is the main thread I know of for the greddy actuator upgrade, atleast it's the biggest one I know of.
https://www.miataturbo.net/forum/sho...eddy+wastegate
There's some good info in that thread, and I just found something I hadn't seen before. Post 44 by AbeFM explains why boost can drop off in high revs -- it's because the IC and piping resist more when the flow is higher, and if your wastegate can signal is hooked up to the compressor, it relieves pressure at x psi regardless of flow. So up top when you're flowing more, you see less boost at the manifold, since a bigger share is lost between it and the compressor.
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