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

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.

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.

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 shit.

Smart to be cautious.

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.

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.

yeahhh mannn you should totally bump ur timing and increase boost cuz it'll b fasterzzzz, fuck motor safety mannn :jerkit:

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.

Bump up your timing or you'll start melting shit. It will also help with your low end. You should also think about adding a decent downpipe and exhaust.

Whatever you do, just listen for knock and watch your OPG. Twitching under load means knock.... Its like knock knock, who's there, predetonation... fuck.

Post pics of the IC setup.

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.

huh?

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

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?

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.

the lower the timeing, the higher you EGT's, thats why Ben said you were going to melt shit.

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.

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

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.

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.

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:
http://i175.photobucket.com/albums/w...os/Picture.jpg
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...

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.

Just remember, you should never hook your WG signal line to the manifold after the throttle body. Heavy vacuum when the throttle is closed will pull the diaphragm the wrong way over time thus damaging it.

Ooook... very strange, I didn't touch the car at all and got in it today to go drive around, got on the gas in second gear and saw 7 psi... but the car doesn't really feel faster than it was....??? Did several pulls, no pinging, deffinately 7 psi and tapers to 6 psi near redline... I DIDN'T DO ANYTHING TO THE CAR... It's like it woke up today and decided to work... but even more odd, it doesn't feel any faster than it did when the gauge was reading 4.5 psi.
GAGH!

What port is your boost guage hooked up too? Was it colder outside. If your AFRs are overly rich that couple extra PSI won't feel that much better due to the overly rich mixture.

The vac line for the gauge Tees off of the vac line coming out of the top of the IM right after the TB. That ok?
Yes it was colder, and the car was not as warmed up as I normally wait for it to be before gunning it.
Don't know about A/F - the wideband is in the kitchen right now...

I was poking around your car while you were sitting on the grid waiting for your runs.

Definitely get rid of the stock weaksauce DP and go 2.5 inches all the way back like BenR and Gay-dar suggested. That will have the most impact on your spool. Not much to add about the GReddy wastegate. That shiznit needs to go.

about helper springs: how strong does the spring need to be to help hold the wastegate closed during spool? I picked up a small spring from home depot and it doesn't seem to be helping.

It needs to be a pretty beefy spring. Judge it by the tension that the wastegate can has, you'll want it to be heavier. When I used one on my Greddy I made it adjustable so I could tweak it. Got a very consistent 9psi on it with out a boost controller.

You could also shorten the actuator rod or shim the can to create more tension, but then you risk boost creep because you've limited the amount of travel of the wastegate.

You positive you don't have an exhaust leak BEFORE the turbo? When I had one I unplugged the signal from the wastegate can and couldn't boost more than about 6-7psi. The exhaust leak was really inconsistant too, one day I could do 9-10 psi, other days I could barely make 6psi. Once I investigated it was clear.

Regarding the helper spring, check this thread from awhile back:

https://www.miataturbo.net/forum/sho...=helper+spring

The Home Depot part number and specs for the spring I used on my GReddy set-up:

SP-9608: 11mm x 6.4 cm x 1.2mm, 11.5 lbs

Some of the coils had to be stretched out a bit or boost would easily hit 15 psi. It worked fine, but over time metal fatigue on the spring just caused the boost to drop again. I'll tell yah, frustrations with the GReddy wastegate was one of the reasons I finally just gave up on the system. I'd suggest just looking into a wastegate replacement now rather than messing around with helper springs and all that.

I've got a brand new wastegate actuator that can be modified (Joe Perez has a thread on it) to work with the Greddy.

It's this one:
http://www.flyinmiata.com/index.php?...umber=02-70576

$40 + shipping

Dang, thanks everyone for so much great info in one place here.

FHS - I saw the spring you mentioned at Home Depot but thought it looked too stiff, bought a softer spring, tried it and it does nothing lol. I'll be going back tomorrow to get the same one you used.
A helper spring is by no means an end solution for the situation, but I'll try it and see how it goes.

This peaks my interest a whole lot - as it is, my actuator is shimmed (washers) farther away from the wastegate - same effect as if I shortened the rod. I kind of thought in my head that would effect how the wastegate opened/how much... could you elaborate a bit? I don't actually know what the definition of boost creep is. As of now, with the spacers, it jumps to 8 psi then drops back down to a steady 7 psi and tapers to 6 psi at redline...

As for exhaust leak pre-turbo, that could only be happening at the head to manifold point or between the turbo and manifold... these two locations are held together by a lot of large bolts that are torqued quite a bit... how could it be leaking?
Could a post-turbo leak effect things? I didn't have the proper size bolts/nuts for the connection from greddy DP to stock lower half DP so I used what I had which were still grade 8 but smaller diameter than should be used there. So, I suspect the two halves of the downpipe aren't mated together very well...


-Ryan

Boost creep is when you overboost due to the wastegate not allowing enough gases to bypass the turbine. It's either caused by not enough wastegate travel or poor flow through the wastegate opening. Common things done to cure boost creep include fixing the wastegate travel, porting the wastegate opening, and getting a smaller exhaust.

You won't have to worry about boost creep with the Greddy unless you mess with how much the wastegate opens.

An EXHAUST leak after the turbo won't affect spool.

God I'm a freakin turbo encyclopedia.

But it will directly effect manifold pressure and thus what the engine gets and the boost gauge reads.

Exhaust leak.

He's talking about between the turbo and downpipe, I didn't clarify.

Yeah an intake leak after the turbo would be bad.

Adding that to my post.

Oh gotcha.

Gotcha. I'm going to go home and remove the spacers between the bracket and compressor and then see what happens now that the car is miraculously doing 7ish psi instead of 4. If I lose too much boost, I'll try to mount a helper spring...

So a helper spring is basically a more ghetto version of a manual boost controller? Or do some use a mbc with the helper spring? Do they cure different issues?

I also need to get correct size bolts and sort out my downpipe connection... I would reallllly love to get a new DP but with the 700 I'm saving up for megasquirt, another 100+ for injectors, the 200 I just spent on alignment and mounting new race tires, 300 I'm spending in a week to get Shaikh's Fatcat adjustable spring perches, and assorted little stuff I'm kinda maxed out (not credit - I don't use credit) maybe I could find a local place to fab something like urgaynknowit did...

-Ryan

Zombie threaaaad. I was just wondering... how about with an MBC? A ball and spring MBC works like a check valve, doesn't it? That should keep the diaphragm away from most of the vacuum, I figure.