might be a really dumb question, but i was in the shower and i thought about this lol.

Ok so i just bought some ctr pistons for my jdm gsr motor. but then i thought, whats the difference between the jdm gsr and itr motor? in the jdm b18c's are the blocks the same and they just have different heads? id much rather rock the itr's if theyre the same.



thanks!

 

the blocks are the same, but they are also the same in north america, the itr just gets a 5 stamp. the ITR crank has a better balance. the JDM rods are p72, not sure if more was ever done to them. the jdm itr pistons also have a larger dome to equal the 11;1 compression, heads have similar flow and the itr manifold and cams are superior. since the ITR is often only 500-700 more than the gsr it's not a bad deal. the cams are $300, intake $150, TB at least $100 and pistons would require a tear down to change. oh, and the better valve train. if your goal is 200 crank hp the itr is the cheaper route. each engine has a purpose, i just really have no idea what yours is.

btw, ctr pistons are one of the worst choices you can use on a gsr head. the compression will be above 12:1 and have a violent swirl in the chamber, this means easy detonation. itr or p30 pistons are a much better choice.

 

Highlights of B18C Spec R compared to standard B18C GSR

1. Camshaft - Wide-angled, high-lift, high-durability camshaft
2. Exhaust Valve Spring - High-lift, dual-layered spring
3. Spark plug - High-heat-type #7 platinum plug
4. Engine Stiffener - Aluminum die-cast, high-durability, one-piece type
5. Crankshaft - Full-counterweight, 8-weight, high-output, custom crankshaft
6. Connecting Rod - Custom TypeR rod, high-durability, lightened
7. Pistons - High-compression, low-friction, custom pistons
8. Inlet Valves - Lightened inlet valves
9. Intake Manifold - Custom tuning, single-port type.
10. Throttle Body - 62mm wide-mouth throttle body.
11. Inlet Valve Springs - High-lift, flat-surfaced, dual-layered spring
12. Port Buffing done by hand
13. Fastening of Connecting Rod done with micrometer
14. All stainless steel headers

 

thanks a lot. yea i know about the ctrs. im wanting 12:1 or maybe higher. but then thats why i thought that if my block already has the itr pistons then ill just go with those cause i know that theyre better, especially if im still going to daily it.

 

12:1 can be done RIGHT on pump gas if you have

1. large cams
2. a reshaped combustion chamber via endyn
3. forged and coated pistons {mahle or rollerwave}

with cast pistons and stock heads over 12:1 means you pull timing in the map. this turns mpg to **** and normally also goes with a rich tune. you can run 11:5-1 all day with cast pistons, stock head and whatever cams if tuned and make within a couple hp of 12:1 on race gas, get better mpg and not have to worry about octane all the time.

 

yea i lanned on all that, itd pretty much just be a weekend reemer. but idk if i can let it sit around cause i love the car to much lol thats why i was wondering about the jdm gsr having the same block as the itr so i can run a safer dd and still have some good umph to it.

 

ITR Pistons are a little weak at 11.1CR in my opinion. I'd personally recommend going with the B16s or forged with a little higher CR and getting a little larger cam to go with them. If done right, you'll make more power and have the same fuel economy. I remember a dyno from awhile back w/ a poormans R vs a GSR w/ 12:1 CR and S2S2s and the GSR made more power across the entire powerband and as I recall got slightly better fuel economy (however it was in a stripped car, so the chassis weight might've played a role there).

 

that chassis weight may also be part of why 12:1 worked on pump gas. along with the obvious tune vehicle weight plays some part in how compression friendly a motor is. street bikes are a great example of this. another thing you can do is have endyn reshape your head. still 11:5-1 can be ran all day with no problems; mpg actually gets better with more compression as long as you don't take it up so high the tune HAS to be rich or uses little timing. i don't think anyone is debating being able to get more than ITR power with more compression, cam and manifold; it just comes down to cost. the jdm itr is a fast drop in that requires no machine work, no hunting for a good shop, no oops the ground my cam wrong issues and no waiting. imo the itr is a great DD engine since the cam profiles are easy on the VT and it makes decent power.

on a side note. there have been more than a few dyno tests of a stock 98+ jdm itr with endyn bumpstix and the matching VT installed providing 200whp. this isn't really a suggestion, just food for thought.

 

thats when you know your obsessed..

 

You seem to be pushing Endyn products(not knocking them down), but:
2. or any other competent head porter, combustion contraption, rlz, etc.
3. again, or any other well known piston manufacturer, cp, wiseco(I know the rollerwaves are Endyn spec wiseco's), etc.