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Old 02-11-2001, 12:04 AM   #1
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Talking Important information/data about EGT probe placement!

Well,

We finally got the EGT probe moved from my turbo up-pipe today. Looks very clean and professional. They already had a y-pipe there that they preinstalled the bung into, then traded my old headers for theirs with the EGT bung. (thanks burninrubber!) It was previously about 2" before the turbo on the up-pipe, and was moved to about 1.5" - 2" off the #3 cylinder exhaust port on my MY00 with JCS IHI turbo RS GB kit. If you have EGR on your intake manifold #4, like some older models, then you want to use cylinder #4 according to JC Sports. They actually say they have seen more problems with cyl #4 in the past.

I was having a dilema tuning the fuel pressure with my Bell RRFPR for full boost, because they told me that the EGT were about 250 degrees colder on the up-pipe, and they were telling me to limit max EGT's in the up-pipe to 1200-1300 degrees. The problem was this temp range felt too rich after I tuned the fuel pressure, and the car ran better when I would let it climb to 1400+ or more at WOT.

So, tuning it to the temps I was told above, at 5 psi I could not pull past 5,800 rpm without bogging down under boost. At 7 psi the car ran great, but EGT's would hit over 1400 and climbing, and I was worried I was over 1600+ at the exhaust port and at dangerous levels. I needed to know that the 1400 EGT's in the turbo up-pipe were actualy safe - And, since the car ran fine and the plugs looked good, I suspected it was okay.

Well, they were partially correct about the 250 degrees difference And I am more confident in tuning my turbo now! It is a bigger point spread at idle, and a SMALLER point spread at WOT under load. Hurrah! Here is the data...

The EGT's at idle in my home garage were always about 500 degrees with the probe still in the up-pipe, and are now between 700-900 degrees at the head, depending on whether I was idling inside the JC Sports garage or parked outside in 25 degree weather.

The EGT's under steady cruising between 2.5K - 3.5K rpm at -15 to -1 vacuum are 100-200 degrees colder on the turbo up-pipe (2" before the turbo) than at the head (1.5" off the exhaust port). For example, I would be cruising at 65 -75mph at -15 vacuum with the EGT's in the up-pipe at 1150-1200 degrees, and now they are 1300-1350 at the head.

But, as exhaust gas flow rates increase above 4,500 to 5,000 rpm cruising in 5th gear under vaccum OR at WOT, the EGT's on the up-pipe more closely approximate those at the head! They are within 75-100 degrees at that point, between those two locations. For example, I used to be at 1,300-1,350 degrees at 4,000 rpm at 90mph at -10 vaccum with the old probe location, and am 1,400 degrees at the head now. In 5th gear at well over 100mph at WOT with boost at 5 psi and creeping to 7 psi the EGT's previously would hit 1300, and now at the head they read only 1400 max! With boost set for 7 psi and creeping to 9 psi under load in 5th at over 100 mph, EGT's never broke past 1500 degrees no matter how hard I tried, when previously it would read 1425 in the up-pipe. I could feel that I was starting to run out of fuel at 9 psi, and now know I could add a little more fuel with the RRFPR to get to 1450 EGT if I want to. Of course, doing that seems to make it too rich at only 5 psi...

This confirms I my thoughts that I am too rich at 5 psi, and okay at 7 psi with my current fuel, and slightly lean at 9 psi. The RRFPR does a good job of supplying fuel, but doesn't seem to adjust to changing boost levels as much as I would like. Stay tuned for my next installment when I get that Simple Digital fuel injector controller with two 440cc injectors in the TB instead of the RRFPR...

Hope this helps - especially those who order a turbo kit with EGT preinstalled in the UP-pipe.

Larry www.ImprezaRS.com
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Last edited by ImprezaRS dot com; 12-29-2001 at 01:28 AM.
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Old 02-11-2001, 12:46 AM   #2
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Very interesting data. What did you do to cover the location where the probe was previously mounted?

My probe is mounted on the up pipe, but an ich or two past where it bolts to the headers. I have never seen a reading above 900 degress, so I am very curious to see what readings I would be getting with a more conventional probe placement. I may move it to a more conventional location soon for peace of mind purposes.
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Old 02-11-2001, 01:10 AM   #3
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The old EGT probe bung on the up-pipe was covered with a fitting removed from an old braided steel line, they welded the nut closed on one end and capped it off.

We were thinking of doing two EGT probes, and having a switch between them, but we'd need to calibrate the two probes to know if they read the same at the same location first. EGT probes can vary in readings by up to 10%. By re-using the same EGT probe in the new location, my data was more valid. And, we didn't need to re-wire anything, I had enough extra wire to move it from the up-pipe to the #3 header.

You might want to have your probe calibrated. Even this guy Brian in Denver with EGT's AFTER the turbo (on the down-pipe of his MY00 turbo) sees 1150 degrees max. They say you lose 250 degrees in the turbo, so his sounds about right vs my up-pipe location.

Larry www.ImprezaRS.com
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Old 02-11-2001, 04:21 PM   #4
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This is really valuable data - I hope nobody misses this post...
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Old 02-11-2001, 05:41 PM   #5
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Well, you guys could've avoided all this trouble by putting the probe in an established location in first place.
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Old 02-11-2001, 07:21 PM   #6
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I requested the standard location, but was "surprised" when I picked the car up that it was in the present location.

You smart @$$ Ridinlow

[This message has been edited by AaronB (edited February 11, 2001).]
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Old 02-12-2001, 05:03 AM   #7
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Larry ~~ I'm surprised that JCS keeps talking about cylinder #4. For the last couple of years I've repeatedly heard stories about cylinder #3. Cylinder #3 seems to be the one that runs the leanest. Even the UK and AUS guys have seen this.

Steve
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Old 02-12-2001, 06:42 AM   #8
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Larry,

I think you will be very happy with the SDS additional injectors, I look forward to hearing the results.
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Old 02-12-2001, 10:28 AM   #9
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Yeah - JCS might be a statistical abberation with cyl #4 breaking more. None have gone recently, but five of us JCS turbo owners lost our trannys in the past few weeks - usually second gear main shaft, one 2nd gear pinion shaft only, one shift fork snapped with bad synchros, and one bad autotranny...

I am happy with the cylinder #3 position I got, but they say do #4 EGT if you have EGR on the intake manifold.

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Old 02-12-2001, 10:46 AM   #10
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Larry ~~ What MY are all these transmissions? Just curious.

Knock on wood, my tranny seems to be doing just fine on my MY98. I've put 25K miles on the car with the turbocharger. Had boost problems for a while where the car would hit 16psi. Have run 1/4 mile, autox's, and road courses.

Steve
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Old 02-12-2001, 01:56 PM   #11
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Both of Dave Scott's broken trannys were Version 1, like a 1996 for the shift fork and a 1998 for the 2nd gear I think.

The auto tranny I have no idea of the year, and I don't know about Mark's car year tranny either. Maybe JCS will tell you.

Larry
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Old 02-13-2001, 08:05 PM   #12
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I was hoping this info would very helpful to people who buy a turbo kit and find it is easier to have the EGT bung pre-installed on the turbo up-pipe and who didn't have a shop nearby for placing one on the header.

I am so much happier now that I have an idea of what my EGT's are. With EGT in the uppipe I was shooting for the wrong numbers. Now, we know what the difference in temps is between up-pipe and header #3.

Larry
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Old 02-14-2001, 12:47 AM   #13
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Thank you, thank you, thank you! I can't thank you enough. My readings are exactly like yours was when you had the probe on the up-pipe. Now I know what I have to do next. I REALLY need to know what my EGT's are when running my NOS and I was already told about this from SteveS. *sigh* Thanks again! Now I better lay off the throttle for a little while.
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Old 02-14-2001, 09:54 PM   #14
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Larry,

Will you simply be using the SDS system to control the additonal two injectors and the remaining fuel supply via the stock ECU?

If so, how much will/did the whole SDS system and associated appurtanences cost you (if you don't mind me asking).

I am very curious about this option since SDS's shop is about 3 hours south of me so a relatively local performance tuner for my neck of the woods.

Once you install the SDS system, will you be posting the install on your website?
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Old 02-15-2001, 12:13 AM   #15
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Markus - I found the SDS system used for $300 with everything including two injectors. It hasn't shipped to me yet, and I understand it is about $450 for a new one with two injectors, or $600 with 4 injectors.

I have no idea how much more I will spend to adapt the FI bung plate from an integra GSR turbo to my RS turbo. I will try to document it on my site, but we are still a bit wearly after the turbo kit instructions and JCS might not have the time to let me snap of photo of every step and make them wait while I type it up - I might have to pay for the extra time

If the deal falls though for the used one, I'll be begging you to get me a good price on the kit from them
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Old 02-15-2001, 11:28 PM   #16
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Larry,

Although I have absolutely zero pull with the SDS guys, I do know a fella that has used their systems quite extensively on past project cars. Should it come down to that, I'll see what I can do for you. Perhaps a two-for-one deal or something of that nature.

Cheers,
MB

[This message has been edited by markus (edited February 15, 2001).]
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