Ok....a gti-r engine has 8.5 compression pistons, and us spec as 9.5 correct? I know the bottom end of the engine can hold somewhere around 400 hp, this should be the same for both engines....now then, what is the benefit of running lower compression pistons? I assume that 15psi of boost on a 9.5 cr motor will produce more power than one with 8.5 cr right? So say you have both engines(and the us spec is turbocharged), and lets say everything on them is the same, other than compression, whats the benefit of the lower compression? Could you add more boost? and if so wouldnt that mean you would need to upgrade the internals if you were to run over, lets say, 400hp? (or whatever the limit is on our engines).
I guess my main question here is can the gti-r motor be boosted more than the us spec without upgrading rods and whatnot?
Or do they both max out at the same H.P?

sorry for any confusion this might cause. please correct me for being stupid if something is wrong

if you IQ has dropped from reading this im sorry ;)

Originally posted by NuttyNate
Ok....a gti-r engine has 8.5 compression pistons, and us spec as 9.5 correct? I know the bottom end of the engine can hold somewhere around 400 hp, this should be the same for both engines....now then, what is the benefit of running lower compression pistons? I assume that 15psi of boost on a 9.5 cr motor will produce more power than one with 8.5 cr right? So say you have both engines(and the us spec is turbocharged), and lets say everything on them is the same, other than compression, whats the benefit of the lower compression? Could you add more boost? and if so wouldnt that mean you would need to upgrade the internals if you were to run over, lets say, 400hp? (or whatever the limit is on our engines).
I guess my main question here is can the gti-r motor be boosted more than the us spec without upgrading rods and whatnot?
Or do they both max out at the same H.P?

sorry for any confusion this might cause. please correct me for being stupid if something is wrong

if you IQ has dropped from reading this im sorry ;)

As far as compression goes, youre right, and both blocks do need reinforcement after about 400 (424whp is the record on a stock block), there are certain other things where they differ, oil squirters, cool the bottom of the piston US doesn't have that, lower compression, is less likely top detonate, but that is all, really less detonation=more boost, GTi-R also has a completly different head, hydraulic valves, sodium filled valves, and other little things that the US don't have. Thats all I can think of right as of right now...

Now anyone feel free to correct me if I'm wrong, but personally I want to build a 300-400 whp sentra for a street car..thats al I want, don't want to build a racecar, just a quick one...

Actually, I think the GTi-R block has 8.3:1 pistons, the BB ones are 8.5:1.

The GTI-R motor has 8.3:1 b/c of the quench area of the head, the pistons are the same between the GTI-R and BB. Please someone correct me if Im wrong.

ok...so whats the point of having the lower compression if the engine cant produce over 400 - 420 horsepower without internal upgrades anyways?

You can run higher boost with lower compression. Lower compression is especially helpful to those who have low octane gas. You want to run the highest compression you can without getting detonation. And yes, the GTiR pistons are the same as teh BB, its the head that causes the .2 lower cr.

Good topic.

The GTI-R has a mechanical valvetrain, regular SR has hydraulic. I believe the exhaust valves are larger, main cap bolts are stronger. Rods may be marginally stronger. Quad TB's, 54c stamped on the block versus 53J on reg. SR. All DET's have piston oil squirters, larger oil pumps, BB and Avenir have 8.5:1 CR, GTI-R has 8.3:1 CR. Different impedence injectors as well as flow rate. Different turbo's among DET's. There are a lot.

Originally posted by scmser
The GTI-R has a mechanical valvetrain, regular SR has hydraulic. I believe the exhaust valves are larger, main cap bolts are stronger. Rods may be marginally stronger. Quad TB's, 54c stamped on the block versus 53J on reg. SR. All DET's have piston oil squirters, larger oil pumps, BB and Avenir have 8.5:1 CR, GTI-R has 8.3:1 CR. Different impedence injectors as well as flow rate. Different turbo's among DET's. There are a lot.

Yes, but back to the main question what´s the benefit??

I think the benefit of having a GTIR over a US spec motor are:

GTIR have lower compression = larger turbo= more boost= more power (in some cases)

GTIR will also be able to REV higher then Us spec motor cause of the valvetrain. NO MORE BROKEN ROCKER ARMS

The GTIR also have larger sodium filled exhaust valves so you won't burn them out so quick.

The oil squirters, larger oil pumps help keep pistons cool unlike the us spec motor.

Overall to me I think the GTIR is the best bang for your buck.

Anyone correct me if I am wrong...

Doesn't the GTIR have quadruple throttle bodies too?

yes it has 4 tb`s.

i have depated this in my head a million times and i will be bringing a gtir motor back to the states with me cause that motor is the s#$%.

it just has to many benifits.the gtir has beffier rods and bugger rod bearings, 444 injectors stock, also i have seen me some hooked up gtir`s smoke a few stock GTR`S and thats no bs.

if you can affod it get it but the sr20 period is an very well designed motor. just my thoughts. thanks ryanGTR

dude i never opened up anything on my gti-r motor, not for cams or anything. made 424whp, daily driven street killer.

It is true what the point that was made, what benefits do you have if ALL blocks, max out at about 400 whp, You still have to build them equally thereafter, so wouldn't you just keep a US block, for the higher comp(less spooling time, i believe) and price, I mean if I was building a full blown race car then yeah GTi-R here I come but for a ~400whp daily driven car, any block I can get for cheap will work....I paid 297 out the door(just the block) for a JDM 9.5:1 at soshin, in South Gate, CA...

anyone feel free to correct me if I am wrong or stupid...but I do acknowledge that the GTi-R is stronger but 400hp on any block will hold, it would just be a matter of time on which will go first....but on another note 400 horses on a front wheel drive car seems senseless to me anyway...but I am still following that senseless root....400 on a 9.5:1 block here I come:D

great topic guys i have been curious about this for a whyle.. does anyone have any pics of the gtir intake manifold or just the motor as a clip im curious to see the beast

As far as block strength, I think the GTI-R bottom end can handle 475whp easily. The stock DE crank/block with rods and pistons should be able to handle the same thing. The block/crank from BOTH should be good for well over 500whp with pistons and rods.

but i have heard if anythng goes wrong with the GTi-R in comparison to the BB you wont have parts to fix it... caust the BB is close to USDM

I don't get what U mean by modifying the block for more power ? HOW ? what do U do weld like supports to the block to hold it togheter at 120psi of boost ? :P Eighter way, BB pistons are NOT the same as GTi-R ones, I have both sets here- different part #s suggar. From what I was told 500WHP on GTi-R internals is possible, this is what I got. Personally I reather have a 53J block and low port head as its eassier to locate parts for one- it if blows up... shit just get another Soko special and strap a turbo back on it and go... with a GTi-R U almost always run into something that causes it to run like shit. No one has yet done a install without something not working right. By putting GTi-R pistons into a 53J block and 53J head or 64F head U end up with 8.5:1 compression. From what I heard cranks are good up to 700HP from a reputable source. U can get the 54C pistons for like 40 bux each with wrist pin brand new- cost ya like 160 bux for a set of pistons- around 70 bux for set of rings, 200 bux for GTi-R rods, all brand new. And U are set for 500WHP. Why go forged on a street car is beyond me.... this aint no friggn Honda.

Yeah fellas, the GTi-R engine is a facinating machine. I have one stripped down to the block in my garage right now. I'm currently replacing the piston rings, rod studs, bolts, and rod bearings, and recently had a broken exhaust stud (within the bore) extracted at the machinist. I'm also upgrading the head bolts to the ARP stud/bolt kit with a Greddy/Grex metal head gasket. The list of aftermarket goodies goes on, but as far as the internals go, i'm leaving it stock. A year of research says to me that the stock internals are fine. I've taken detailed digital pictures of the head, block, quad throttle body, intake manifold, crank, rod bearing inspection (plastigauge style), pistons etc. But it seems that the website under unlucky's post has all the pics u need =)

hotshotsr20 is about to go for the stock block record, but he's gonna use S3 cams. i'm gonna see what the stock BB internals will do.