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Discussion Starter #1
i am going to do a compression test on my GTI-R motor this weekend more than likely. does anyone know what kind of readings i should get back so i know if i am low or not.

thanks
 

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Discussion Starter #3
man i am hearing in ranges from 130 to 180. i wish i could find a definitive answer.
 
D

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Well 180 is much more the stats from a stock sr20de, with 9.5:1 compression, but a gti-r is 8.3:1 compression....


I tested my BB at 140psi (average)...
 

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Discussion Starter #5
i hear that, i wish i had a fsm for a gti-r so i could look it up and see for sure.

thanks
 
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I agree with 130-140. My DE with forged 300ZX pistons (about 8.5:1 in the SR20DE) made ~140 across the board IIRC. 180 sounds right for a regular DE at 9.5:1 compression.
 

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Ive seen the fsm for the gti-r before but Im not totally sure, I do recall 165 as max i think. Like I told you on the sr20 I hit 200psi on all 4 Wiseco 9:1 pistons w/ gti-r motor.
 

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Icy Hot Stunta
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SuckiT said:
Like I told you on the sr20 I hit 200psi on all 4 Wiseco 9:1 pistons w/ gti-r motor.
I don't think thats posible unless several things were going on.

1. for some reason the pistons were made wrong and the compression ratio is too high, this happens all the time, especialy with motors the piston makers are not familer with and people that don't know how to fill out the custom piston build sheet right which is most people.

2. The cam timing is off with the cams too advanced, especialy the intake cam.

3. Oil in the cylinders for some reason

4. gauge is off. This is pretty common. If you drop the gauge it can get knocked off.

Mike
 

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I read that the Wiseco pistons were originally designed for a RWD SR20 with a flat top design while the fwd is a dish design. Other than that I have no explanation for the high reading. There is no oil in the chambers. The gauge reads 180psi on my friends B16a which is normal. My cam timing was set correctly 3 times before I told my brother ok its fine. Any other ideas on why the high compression?
 

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Icy Hot Stunta
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SuckiT said:
I read that the Wiseco pistons were originally designed for a RWD SR20 with a flat top design while the fwd is a dish design. Other than that I have no explanation for the high reading. There is no oil in the chambers. The gauge reads 180psi on my friends B16a which is normal. My cam timing was set correctly 3 times before I told my brother ok its fine. Any other ideas on why the high compression?
EEK! a flat top, provided that the pin height is such that the deck is zero equals about 10:1 with the SR's 39cc combustion chamber! A GTI-R chamber is slightly bigger, like 40-41 cc's.

Yeah your compression is about normal for a 10:1 motor!

Mike
 

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Discussion Starter #11
thank you guys for all your feedback, i greatly appreciate it all.

thanks!!!!!!
 

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Well my memory still is good, checked again for the gti-r manual and its 164 standard and 135 is the minimum. The DE with a 10:1 is 185 max and 156 minimum. As for my compression results, 10:1!!??? Dang that sucks but what can you do. I was planning to take it out maybe to recheck the internals but if I do should I change the pistons? Or leave it cause its been 6 months and seems fine?
 

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Discussion Starter #13
hey simon, did you buy a fsm for the gti-r? and if you did where can i get one as well?

thanks
 

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No its online, you have to search for it. GGon has some of it but not all of it. The Australian site has it posted at least most of it. The regular SR20 and the Gti-r are totally different as in torque specs. Like main caps are 82lbs/ft and the Head bolts are only 98lbs/ft or 90 degrees from 68? Little differences, Ill help you find the site in the morning. Its also why I have to take mine out cause I think my head bolts are stretched and my mains are too loose since its torqued to the DE specs.
 

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Icy Hot Stunta
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SuckiT said:
Well my memory still is good, checked again for the gti-r manual and its 164 standard and 135 is the minimum. The DE with a 10:1 is 185 max and 156 minimum. As for my compression results, 10:1!!??? Dang that sucks but what can you do. I was planning to take it out maybe to recheck the internals but if I do should I change the pistons? Or leave it cause its been 6 months and seems fine?
What head do you have?

Mike
 

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CA18DET Wizard
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Hey SuckiT I would take it you're running stock boost and a stock ecu, correct? With that type of compression on your SR, you're bound to be detonating and triggering the knock sensor! Did you send Wiseco a sample piston or did they sell you an off the shelf set of SR slugs? You can actually run the car with high compression, but there's going to be alot of baby-sitting if you decide to crank up the boost.
 

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I bought off the shelf pistons that everyone on the forum recommends. It was Wiseco 9:1 pistons for the SR20 but I knew since with the factory 1.2mm gasket and Gti-r head it might be 8.8:1 which didnt sound to bad. To have 9.8:1 would suck...since the majority thats built there motor uses this brand as well. How else could I tell if that was my compression? I have the spec sheet downstairs; would that help? I just thought it was really good rings!!

As for the ecu, im using the JWT 444cc/Cobra maf setup and AFC is set to zero. I boost constantly on 15psi all the time. I have heard detonation before but that was cause my timing was too advanced but not anymore. Other than that the motor feels the same. Egt's are always 750c-800c while cruising tho at 70-80mph. Idle egt's are 500-550 since the idle is at 1000rpm. At WOT the egt's are always 750c any gear. The slugs are coated from Swain if that affects egt's in anyway.
 

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CA18DET Wizard
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One of two things I'd recommend, but first post the specs of the pistons so we can check them out to see what they gave you. If they are high compression pistons, I'd just plain 'ol take them out, sell them (and they will sell) and get the right stuff in there! No playing around with headgaskets heights because from my experiences) that SR don't like to be experimented with. That's a very expensive motor you have and would hate to see you detonate and risk hurting it because you already know it costs to "POP".
 
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