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It was a combination of several sites that gave various info about head volumes and such like. Our UK haynes manual keeps telling us that some SR20's have 9.8:1, so I kept digging to see which version could have that, and the head volume gives 10:1 for flattop pistons in all the versions I could find, you US guys get 9.5:1 with a dished piston, and I was doubtful about an intermediate piston with a smaller dish. Then coming across the GTi-R head volume the penny dropped about the source of this mythical 9.8:1 that I could never find.
Table Of Contents/Index: Page 1: General Info on Everything I Could Think Of | Props from SR20 Forum Page 2: Compression Theory | Physical Differences B/N Regular DE | Efficiency | Power Page 3: Comp. Theory Cont. | OEM vs. Tubular Header | Which ECU? | Water Pump? | USDM IM w/ RR VC | Engine Break Down Page 4: Dyno Testimony | Reg. DE & RR DE VC Compat. | Water Pump Compat. | Power Curve Diff. | Pulleys | Boost Capability Page 5: ECU Tuning & Ign. Timing | 4CW Crank VS. 8CW Crank | Swap Complete | PCV Schematic - USDM IM | 96-99 Almera GTI
What Does That Mean?: IM = Intake Manifold VC = Valve Cover RR = Roller Rocker CW = Counterweight B/N = Between
Thats real interesting... so is this something that you found out by putting two and two together? Or is this information valid factual information? Is there anyway that you could find that out?
So what you are saying is that for a handful of USDM/JDM roller rocker they used a GTi-R 10:1 Head and Regular 9.5:1 Dished Piston's? or maybe I am reading that wrong?
I just thought the pistons on a roller rocker were different (higher rings)... So maybe thats an issue... Could someone verify... This is definitely one of the things that I am a little wishy washy about.
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Last edited by XxToKeSxX : 04-28-2006 at 07:33 AM.
Almost there, what i am saying is that the GTiR with a flat-top piston will give 9.8:1, I am not sure it ever went into a production motor, but haynes ran with those numbers and told us that UK engines are 10:1 or 9.8:1.
The roller rocker I also believe has higher ring lands.
Well try and find a head combination that doesnt give 10:1 with a flat-top piston, if you do I will have to apologise for getting it wrong.
Almost there, what i am saying is that the GTiR with a flat-top piston will give 9.8:1, I am not sure it ever went into a production motor, but haynes ran with those numbers and told us that UK engines are 10:1 or 9.8:1.
The roller rocker I also believe has higher ring lands.
Well try and find a head combination that doesnt give 10:1 with a flat-top piston, if you do I will have to apologise for getting it wrong.
Mike
Well if I had a GTi-R Head laying around here I would , but until then, I think this is one of those things that will be up in the air. I'm glad you said something though because it's not a huge issue, but it still needs to be looked into. I wish I could argue, but I really just don't know, you might be onto something.
So... If ive got two engines sitting in fron tof me... One RR, and one NONrr... is there anything just by looking at the outside that will tell me its a RR. Is the VC higher, or just diffrently shaped. Im just trying to be able to identify just by looking. Ill go thru and read your posts again more thuroughly. Thanks... and GOOD thread maman.
I am just figuring that if its a newer motor, then chances are its RR engine. I guess ill just look at my engine, and then look at my p11 engine, and look for diffrences, besides the highport lowport thing.... p11 low, my 200-high.
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Last edited by LucinoSR20de : 03-08-2006 at 07:54 AM.
So... If ive got two engines sitting in fron tof me... One RR, and one NONrr... is there anything just by looking at the outside that will tell me its a RR. Is the VC higher, or just diffrently shaped. Im just trying to be able to identify just by looking. Ill go thru and read your posts again more thuroughly. Thanks... and GOOD thread maman.
I am just figuring that if its a newer motor, then chances are its RR engine. I guess ill just look at my engine, and then look at my p11 engine, and look for diffrences, besides the highport lowport thing.... p11 low, my 200-high.
Look at the bubbles that portrude out on the valve cover. If it has bubbles around the valve cover it is an RR motor (the valve covers are also much taller), the non RR motors have an indentation marks around the valve cover. The VVL motors have the same cover.
I think what needs to be understood is that the Primera GT has 10:1 compression due to the pistons, the non GT 2.0's are probably like you stated if it says it on the Haynes manual its 9:8:1.
Cool... thanks dom... and toke, for the very informative information. This is why I love these forums. Anything i wanna know... I can learn from everyone.
Another question... Ive always heard that RR motors are a lot better then NONrr motors, in the sense of power, and efficentcy. I know that i had a full RR motor in my 72 chevy P/U, and it was a lot tougher, and a lot beefier, and could handle mroe power then a regular camed motor. Maybe i just dont know(still) what im talking about. Is this the same for imports... or a diffrent story all together?
Well RR reduces the losses in the cams, but there are some weaknesses in how high you can rev some of the rr variants. Having a spraybar engine myself I havent seen the RR up close.
The roller rocker engine was designed to be more efficient, but I believe that the only real restrictions that are involved with some of the RR SR20 are because of the high ring lands on the pistons, and the weaker valve train. I think that this can be compensated by upgrading it.
Like Mike (UK-SRi) said, the roller rockers free up the friction caused from cam lobe/rocker rubbing. Instead of the actual lobe hitting the stamped rocker, the lobe 'rubs' on the roller....
I have a RR with 2J2 on top head towards driver side. Is that good enough for me to think that it is 10 to 1? or do I still need to confirm dish/flattop. Here is the picture. Its not really that clean however has the bubble that Domiken mentioned.
I have a RR with 2J2 on top head towards driver side. Is that good enough for me to think that it is 10 to 1? or do I still need to confirm dish/flattop. Here is the picture. Its not really that clean however has the bubble that Domiken mentioned.
There is actually a contradiction as far as the compression goes for roller rockers.
If it is a USDM engine I have a question for you: Is it a G20 or B15 Engine?
I think that is the deciding factor because according to what the contradiction is saying: 2000-2001 B15 have 9.8:1 ... and 2002 G20 Motors have 9.5:1.
For some reason this is all understood. The FSM shows small differences in timing also. Check out the first post again... This is wierd. Some of that info can be found in TUNED200's "Soko" post.
i agree, theres a very big possibility that i have the engine with the 9.5:1 compression. given that fact, are there JDM SR20Di or JDM SR20De engines that look very very similar to the normal RR sr20 primera engine? i asked coz id have to kill my supplier if i get one of those. hahaahahahahaha
btw, i also heard somewhere that there have been rumors that a jdm engine similar to the black sr20 primera gt has been released, the only difference being that these engines have silver/grey valve covers. can anyone verify this?
This bites. Unfortunately, I bought the car with the RR motor in it (just two weeks before buying). I just sent my ECU to JWT for reflashing and told them 10 to 1. Now I am worried that might not be true. The guy I bought the motor from did not know where the motor came from as his friend assisted with the install and motor buying process. 2J2 on side of the head was my only hope to get a compression number matched with. The car had an unusually high timing of 23 degrees (stock pulleys). I lowered it to 15 due to potato.
On another note, what is the number on my valve cover with a permanent marker saying "742685A". Is there any hint in there
I do not know if this is a JDM or a USDM (anyway for me to tell?). The oil filter is also towards the back hanging down rather than it being on the passenger side wheel and side ways. Are these limited to what ECU can be used? It turned on with a 94.5 G20 OBDII ecu. The more I dig into this, more questions arrive. Sorry!
hahahha i think we have the same prob bro. the only stamp i have of mine are that of 1R 2J2. how bout you, does your engine just have the 2J2 stamp? try to take a look underneath your exhaust manifold,on the block. let me know if there's a hidden stamp there or something._
I did find a 2J2 stamp on the side behind distributor embossed from factory. However, did not see 1R anywhere. I will look for more... even then how to figure out the compression numbers
, but until then, I think this is one of those things that will be up in the air. I'm glad you said something though because it's not a huge issue, but it still needs to be looked into. I wish I could argue, but I really just don't know, you might be onto something.
