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Discussion Starter · #1 ·
hello everyone i am the ls motor that has je 10.5 cr pistons,eagle rods,arp studs, crower 403's,springs and retainers,aem adj. cam gears,aem fpr and gauge. and i pulled max 152.9whp and 124.7 wtq... well since i am not happy with the power output i am going to sell my je pistons and i am going to buy civic type r pistons and rings that yeild a 12.0+ cr in my ls. along with my skunk 2 intake manifold, and 4-1 header. i will also upgrade my oil pump to a gsr oil pump because i have my redline set to 8000rpm... i am upping my compression 2 points and am going to focus on the top end or peak whp. since i am going to up my cr 2 points i think i should see the gains that i was expecting from the beginning. and have my safe built ls motor that i wanted from the beginning. can you please give your input. thanks again.
 

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what would you be satisfied with ? (i.e. make you happy realistically)


As I said to you in our discussion tuning the fuel is a huge part of making the car driveable and perform. A stock ECU on a 310 injector would run horribly if left untuned. You'd be washing out your cylinders and lowering your ring seal.

I don't know why you went to a 310 but since you already have it, you must lean it down sufficiently. A stock 240 injector flows enough for 175 whp with adequate FP settings.

Having too much fuel will protect you from detonation but the burn efficiency is negatively affected even with 10.5:1. So reading your WOT af ratios from 5000-6500 rpm in an LS revving to 7000 rpm is important.


The second limitation to top end power in an LS is it's head. The head is what sets your peak potential. If you can't flow enough through the ports, it doesn't matter how much cam you add.

you need to have enough air (also called mass flow, flow volume, flow capacity) to make a certain peak hp number. If the head can't get you that much air, you won't meet your expected peak goal no matter what you spend.

The IM upgrade should help.

The 12:1 CR: why are you going so high?

here's some useful info from 2 sites you can apply:

Cams for B18B1 / B18A1

bore 3.1889 in., stroke 3.504 in., rod 5.394 in. ,0 boost, 600 ft altitude.

Dynamic CR calculator

cylinder pressure (psi)% change from stock

stock 181-

Crowers &
10.5:1 20312%

Crowers &
12:124133% !!!

That is seriously undercamming the motor and would blunt your top end (> 26% increase in cylinder pressure). You'll get a gain from the burn efficiency increase of 1.5:1 CR (assuming proper fuel tuning and adequate mass flow) but the undercamming will lower it's potential (expected power from CR increase is 1% per 0.1 increase until you undercam = 175 peak whp).

11.0 to 11.4 static CR would give you a 20 to 25% gain in cylinder pressure (recaptured) and all you need.

using skunk2 high CR valves and a thinner headgasket would get you there without having to swap the pistons (as long as your walls aren't washed out and ring seal affected by those 310 injectors).

If you fall short, you'll know where 2 potential sources are.


getting a 4-1 will help your top end.
 

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Discussion Starter · #3 ·
i'm not running a stock ecu... its a fully programmable ecu sort of like the hondata... my realistic goal would be 165+whp.. is that too hard to reach with the ctr pistons 12.0+cr,crower 403's,skunk 2 manifold,i/h/c/e?
 

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Steven, maybe you aren't reading MD's posts. You will be seriously wasting your time by bumping up to 12:1. Ideal cranking pressure is between 16-25%. You would be at 33% w/that setup. The crowers will run out of breath and the LS head will need to be ported to flow more. I say that if you are really that committed to making 13whp you would look into something other than those new pistons, like maybe a b20 or a full hytech exhaust. Like MD said if your hell bent on bumping up your CR go with the skunk2 valves and a thinner headgasket. I think that you're focusing too much and making peak power when you should be focusing on making your car faster.
 

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Discussion Starter · #6 ·
well what pistons would yeild a 11.0-11.4 cr in my ls.... so i can stay inside that 25%? and what would skunk 2 valves do? basically what is left to do so that i can make more power. should i put on the skunk 2 im, and 4-1 header? my redline is at 8000rpm so i can rev pretty high. i just need help. thanks guys.
 

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i think you should have researched more before you put that money work into your engine...imho
 

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water under the bridge Andy. he can't hit the rewind button and so it's sort of not gonna help him telling him that now.

You can use P30 pistons with your LS rods to get 11:1 (you can decide if you want to risk the non-bore-honing and use the 81mm size or go overbore 81.25mm size) . Add Skunk2 standard sized flat face high compression valves and they bump up the CR by about 0.2-0.3:1 with your cylinder head. But this is not mandatory. In fact you could just go with a modified 2 layer OEM headgasket and use hondabond #4 to get your 11.3:1 without changing the intake valves & valve guides. This is optional.

The PR3 pistons also fit the LS rods but yield 10.8:1 and would need the thinner head gasket or flat faced intake valves to get you over the hump to 11:1.

If I was in your boots? I'd send the head in for porting to flow enough for 175-180 whp and add new valve guides and use the Skunk2 valves to bump your current JE's setup to 10.8:1 and use a thinner headgasket.

2 things to check before going that route:

1. the diameter of the JE piston's intake valve reliefs (the pockets on the dome of the piston for the valves, check the larger intake side diameter) , to see if they are big enough for VTEC intake valveface diameters (i.e. the Skunk2 valves).

2. compression test your motor to see if your ring seal is still nominal.

if the ring seal is shot, then this idea goes out the window and plan B would be to swap out the pistons or change the rings.

if the piston valve reliefs are too small you'll have to get them to open them up.

using this approach you don't have to spend money on new pistons and piston install for the CR bump you need and put that money into increasing your engine's ceiling potential which is governed by the head's flow capacity.
 
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