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Old 01-21-2004, 04:04 PM   #1
AZScoobie
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Default Headers, manifolds and tuning.

Since I installed my Type RA engine last may I have had a Set of GTspec Headers on my car. These where the original version with the 2 bolt upipe. I ran these headers with a PE1820 and with my current Garrett GT30R turbo. A recent trip to the dyno showed some serious lag out of the garrett:




14 psi by 5200 rpm. On the road in 4th gear WOT at 3k rpms I would get 14 psi by 4600-4800 rpm. This pull was untuned. I did not have much time on the dyno as it was a dyno day...

Further tuning got that down to 4600 rpm at best. I decided to go back to stock manifolds in hopes of improving this lag.. I obtained all the pieces I needed to go back to stock from some of the guys on the boards and got to work. I started by bowl porting the inlets to the cast manifold sections. I simply traced the gaskets and then ported the entry down in the shape of a bowl or flare. I used a Dremel with a Grinding disk. Very easy to do... Wear a mask though.. I still blow out black not even days later.

I then bowl ported the crossover pipe and exit to the upipe. The upipe was wrapped.

First thing I noticed was the exhaust note was back to being deep and bassy. No more higher pitched sound.

On the first trip out with the stock manifolds I was disapointed. I had MORE lag then before.. 5400 rpm to get 14 psi on the road. I had my wideband in the car and noticed things where lean.

I spent a few hours tuning the car with the wideband and the ECutek flash software for my JDM ECU. I was shocked at how much Fuel I had to ADD to the map. I had to add a full 8% in fueling across the board for the AFR corrections to come back inline and for my open loop AFR's to be on target. Very odd... I cant really explain why this happend. Nothing else was changed. I need more fuel to obtain the same exact AFR.

Bottom end power is much better now. The car runs smoother and that damn anoying flatspot is now gone. I am getting 14 psi by 4000 rpm or so now that I am tuned. I cant comment on the top end power because I cant tell and I have not had it on the dyno. The Road dyno on Delta dash shows more power. My suspect is that I lost some top end but gained bottom end.

Another interesting thing to note is on the subject of EGT...

With the GT Spec Headers I had the Greddy EGT probe mounted in the #4 cyl. Cruise EGT was 700-710C. WOT pulls netted 750-760C tops.

I now have the probe mounted on the casting button so #4 and #2 flow across the probe. EGT is much higher. Keep in mind the same fuel, boost and AFR and the same advance as before. Cruise EGT is 800C to 810C depending on RPM. WOT EGT is 850C and in a long 4th gear pull it nears 900C. I am not worried about that as a temp but the interesting thing is that my EGT gauge now reads a Solid 100C higher then before.

Anyone that has ever pulled stock plugs on a JDM STI EJ207 engine will tell you that Subaru installs a hotter range plug in #4. A heat range 6 and the rest of the cyls get a heat range 7 plug. I have to assume this is because #4 for some reason Runs rich in comparison to the other cyls. I am going to install a hotter plug in #4 because I know its much cooler then the #2 cyl that I am now getting that excess heat from.

Dyno plots to follow soon... I need to pick up some good fuel and fill the nitrous bottle. That 370 pull was on some C16 tossed into a Tank of 91 octane and no nitrous. I want to break 400whp on that dyno.

Cya

Clark



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Last edited by AZScoobie; 01-21-2004 at 04:09 PM.
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Old 01-21-2004, 05:47 PM   #2
Need4Boost
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Default Re: Headers, manifolds and tuning.

Quote:
Originally posted by AZScoobie

I now have the probe mounted on the casting button so #4 and #2 flow across the probe. EGT is much higher. Keep in mind the same fuel, boost and AFR and the same advance as before. Cruise EGT is 800C to 810C depending on RPM. WOT EGT is 850C and in a long 4th gear pull it nears 900C. I am not worried about that as a temp but the interesting thing is that my EGT gauge now reads a Solid 100C higher then before.
Very interesting. Maybe the heat from both cyl 2 & 4 caused this?

Quote:


Anyone that has ever pulled stock plugs on a JDM STI EJ207 engine will tell you that Subaru installs a hotter range plug in #4. A heat range 6 and the rest of the cyls get a heat range 7 plug. I have to assume this is because #4 for some reason Runs rich in comparison to the other cyls. I am going to install a hotter plug in #4 because I know its much cooler then the #2 cyl that I am now getting that excess heat from.
Now this I did not know about my RA-C. Thanks for the heads up!

Quote:


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Old 01-21-2004, 06:21 PM   #3
cronic
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Interesting info on the changes made by the headers.. I was always under the impression that the headers didnt make much change to AF and didnt need tuning..

Dave
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Old 01-21-2004, 08:56 PM   #4
Kostamojen
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The EGT makes sense, since with a higher flowing, less heat saturating header, it would be colder. Stock headers are huge chunks of metal that just suck up heat like a sponge, and without equal length and the 4-2-1 style makes all that heat show up closer to the block as well.
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Old 01-22-2004, 01:18 AM   #5
hao
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Default

Hey Clark sounds like a very interesting and fun project you got going on.

If you don't mind I would like to pick your brain on some of these ideas about your higher EGT's and why cylinder #4 uses a hotter plug.

I've never played with an RA motor but what cylinder is the knock sensor mounted on?

Have you tried remounting your EGT probe in the same location cylinder #4 as you did for the GT-spec headers and then compare temp values? What distance in inches from the head was the probe installed at?

In regards to the different spark plug, I think (and this is just a theory) that Subaru uses a hotter plug in #4 because it is the first cylinder in the fuel rail to see pressure. Of course this will need to be verified by measuring pressure drop across each injector in the rail.(But who really wants to do that?)
If cylinder #4 theoretically has a higher fuel pressure than it can inject slightly more fuel than the other 3 injectors down the line (higher pressure same pulse time usually results in more fuel).
But the question comes down to why the EJ207 runs different plugs? (maybe someone from Subaru can answer this?)

Another thought might be to run some new plugs drive around with some good engine pulls and then pull out the plugs to look at the color of the plugs. Personally I still think its the best way to make sure all cylinders are running well, its the window into the combustion chamber.

Let me know if this makes any sense to you, or if you think I'm an idiot.

Hao
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Old 01-22-2004, 07:01 AM   #6
TheMadScientist
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I did the same thing with my TD05. With headers I would get 17psi ~4000rpm. I did what you described and bowl ported all the flanges that had flow going into them. After I reinstalled the ported stock headers I was getting 15psi at ~3000rpm and 20psi by 4000rpm.
When I get my Sti this will be the first thing I do.
TMS
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Old 01-22-2004, 05:08 PM   #7
03WRXMA
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I am very interested to hear more info on the plug change....
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Old 01-23-2004, 10:37 AM   #8
TurboRex
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I e-mailed you Clark but for some reason your responses are not getting through. The message says they are infected. Anyway, if you could, give me a pm.

Good info above.

Greg
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