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Old 06-24-2007, 09:06 AM   #1
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Default How high with a Greddy?

I'm in need of some advice, I'm unsure where else to ask these questions, and I know the Greddy guru's on here sure know their stuff

I'm running EMU with 460cc injectors (supposedly), no AFM (removed using Joe Perez's airflow output map).
I've recently been trying to get the boost to stabilise at 15 psi without boost overshoot. If I set the manual boost controller to 13 psi, at WOT it will overshoot to 15 psi then after about a second or 2, drop to 13 psi.
If I set the boost to 14.5 psi, it will overshoot to just over 16 psi and then drop back down after a second or two. This is where its set at now.
I read somewhere that 15 psi is the limit for this turbo, but there is quite a bit more power to be had above that level - a rather noticable difference between 15 psi and 17 psi
It appears that the actuator isn't fully opening the wastegate, literally as though the piston weren't moving the wastegate much as it is meant to swing (lots of extra play). Is this normal?
Can I upgrade the actuator somehow?
I'm considering upgrading to some form of electronic boost control, will this solve the overshoot problem mentioned above?

The afr's are in the high 11's @16 psi, no knock. I've tuned the EMU up to 17 psi (was 16 psi) to ensure no lean conditions or knocking occurs with overshoot. So if push comes to shove, I can live with the overshoot.
The factory 1.6 engine and turbo seem to handle this fine, so far at least.

Also, any idea on how this boost level will affect the turbo long term?
Its only a Greddy TDO4H-15G, so if it goes pop it won't cost much to replace.
I can post datalogs of the AFR's & boost levels if it helps.
Sorry for all the questions at once, but any advice at all would be very much appreciated.
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Old 06-24-2007, 03:16 PM   #2
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Arent there a set of numbers on your injectors that you can verifty they are Rex seven injectors...I could be wrong. but I think someone mentioned it in a differnt thread.
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Old 06-24-2007, 03:32 PM   #3
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Yea, they're RX7 195500-2010's. But sometimes the actual flow is higher than the value stated. These seem to be flowing a bit extra, but I could be wrong.
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Old 06-24-2007, 04:40 PM   #4
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Thats alot of boost.....Wow. 4psi (before my motor went. Dam.) I would spin tires trhough first and second just flooring it from like a 5mph start. with good tires....and like 195's too...how the hell does it feel like with your boost numbers
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Old 06-24-2007, 04:47 PM   #5
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you'll probably blow out the piston rings eventually....even with a good tune, they seem to blow out at around 13-18psi regardless of power.
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Old 06-24-2007, 04:53 PM   #6
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to stabilize the boost you need a helper spring i am doubt full you make more than 270-280 whp with the td04 still that is some nice useable power.
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Old 06-24-2007, 06:28 PM   #7
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Quote:
Originally Posted by tritium View Post
I read somewhere that 15 psi is the limit for this turbo...
Nope, according to the compressor maps that are posted on the S3K forums, it's 24 psi, with 28 max psi.
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Old 06-24-2007, 08:55 PM   #8
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I'd definitely try a helper spring to help out with boost control issues unless you go ebc. The GReddy wastegates are notoriously poor so they need a little help for boost above 12psi or so.

With the stock motor, I would go that much above 12-14psi even with a good tune. It's not to say that is can not be done, but I think that if you drive the car hard (track days, auto-x, etc...) on a regular basis, the engine will wear much faster. My rings were fried b/c I ran 18psi, but I'm pretty sure that the 16 sessions from the two track days at 15psi didn't help much. In general, for a street only car, you probably are not hitting the full 15psi that often and even then, not for very long periods of time whereas on the track you are pretty much in boost and near max boost as much as possible during a 20 minute session.

Yes, the TD04-15G can push more than 15psi, but I think on a 1.6 after about 18psi or so you are just creating more heat than incremental power as your start to get really outside the efficiency range. So on a built engine sure you can run a lot more boost out of the turbo, but you may not be making much more power due to the added heat.

For more power than 15 psi on the GReddy turbo, I'd imagine you would be better off with a built engine as well as a better suited turbo for higher power goals. YMMV.
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Old 07-11-2007, 03:08 PM   #9
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Just a quick update.
I've recently fitted the helper spring, and its working great. Huge difference. Boost overshoot is about 1 psi, which I can live with.
Thanks for the info !
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Old 07-11-2007, 03:23 PM   #10
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Pictures?
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Old 07-14-2007, 12:55 PM   #11
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Default Helper spring







As you can see, this is temporary until I can get a better mount for the spring, but in the mean time this is working remarkably well.
The spring alone holds boost up to 13 psi, the mechanical boost controller must therefore be set to 15 to hold 15 psi. I will probably remove a few turns on the spring so that it will hold 15, hopefully that will minimise the little boost overshoot that is still occurring.
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Old 07-14-2007, 01:21 PM   #12
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Great work glad you figured it out
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