The build:
B18a1 block
Eagle h beams
Wiseco 81.5mm 12.5:1 pistons
Type r oil pump

Gsr head
Supertech valves
Supertech dual springs
Supertech retainers
Skunk2 lma
Gsr cams, golden eagle cam gears
Skunk2 ultra street manifold
Skunk2 70mm tb
Aem fuel rail, RC 440 injectors

Head was milled and block decked by previous owner, unsure of how much.

P06 Ecu chipped for vtec and tuned for 93. I have skunk2 pro3 cams I have yet to install, as well as a p28 with hondata s300 for better tuning




My lsvtec recently started making a lot of engine noise. Sounded like valvetrain, I pulled the engine and tore it down. I found all 4 pistons cracked with chunks missing on the intake side. Cylinders 1 and 4 were mangled, the dome of the piston as well as the chamber on the head. Could this be from detonation? Assuming with the milling it was 13:1-13.5:1, is this too high of compression for pump gas?

 

Could be. That's a **** ton of compression for stock cams, there's a good chance you were knocking in the midrange, while still on the low cam.

Also, I can't say this enough. Current pump gas is **** and is only going to get worse. The days of daily driven high comp engines with no knock control are gone. Sky high compression on a street build is overrated anyway.

 

Was this setup tuned properly? Or just basemap tooned?

 

The existing Ecu was tuned by a reputable shop for this motor by previous owner, and it ran fine even took it to the track. I've only done minor changes, the ultra manifold, tb, lmas, new honda bearings and new rings (from wiseco, for said pistons). It started making noise when it fowled the stock plugs and I replaced with similar ngks, just up a heat range

 

Why did you change and run HOTTER plugs from what it was tuned on? That's what created the issue. It wasn't the gas, it was you.
If it was tuned and ran fine before you changed the plugs...you have your answer. High compression/FI + hotter plugs = big problems.

 

13.5:1 on pump fuel? I'm surprised the tuner even wanted to tune the motor.

 

Okay. I have the hondata s300 to get it retuned, but now replacing the bottom end I may go with a b20 instead of an ls. What compression is suitable for all motor on pump gas? The car isn't a daily, but does get street driven. Also e85 is scarce in my area.

And if I do switch to e85, what all will need changed?

 

Personally, anything over 12:1 on pump gas I feel is too much. People do it, but I would rather advance timing while tuning than gain half a point of compression. That's just me though.

If you run E85 you will need to beef up your fuel system. All components will need to be compatible w/ alcohol based fuels. E85 takes roughly 30% more fuel than unleaded also, so you will need to up the volume.

Upgrade the fuel pump, FPR, injectors, fuel rail, supply and return line at a minimum....at least that is my opinion.

I run E85 on my setup and have the following:

Walbro 255
Aeromotive 1000 FPR
AEM fuel rail
ID 1000 injectors
Devsport upgraded supply and return lines

I also treat my E85 w/ lucas oil ethanol conditioner, it's an additive that "lubes" the fuel system to help protect against the alcohol of the E85.

I may have gone a little overkill, but I have seen what alcohol based fuels do to a fuel system that is not properly setup for it.

IF you plan on running those pro 3's you will want AT LEAST 12.5-13:1 compression, ideally no less than 13:1.

Check out my build thread for ideas

 

Are the 1000cc overkill? My 440s might not cut it, but I am already running -6AN supply line, aem high volume rail, aem fpr. Still on stock fuel pump though. I believe with my head and block being decked there was clearance issues, will a 13:1 b20v have any clearance issues with a different, untouched gsr head?

 

440's most likely will run out of fuel, I had RDX injectors and decided to go larger after crunching the numbers...and that was with them running over 500cc w/ the pressure turned up.

1000's leave more than enough room to grow in case you want more later. There is little to no price difference in the 725's and 1000's so might as well go larger. Less duty cycle the better.

I may add nitrous in the future which would put me at a higher duty cycle on a 725, but will still be pretty damn low on a 1000. Just things to think about.

I would check clearances with pro 3's, they are a BIG cam. You should be ok, but better safe than sorry.

 

id say your compression was substantially too high for pump gas, especially with only gsr cams. I've run a few lsvtecs with type r cams and around 12:1 you have to pull a good amount of timing from the stock maps. Its not just at high load either. light to moderate load, like around 8-12" especially below 3500ish rpm can be prone to detonation according to my knocksense and confirmed by my spark plugs.


did you have a wideband in the car? what was the afr? do you know how many degrees timing was in the tune? did you have an egt gauge?

it would (id assume) take something seriously wrong with the tune, another hidden contributing factor, or just ridiculous abusive driving to wreck forged pistons as you described. do you have pics of the pistons, cylinder walls and underside of the head?

was the motor previously burning oil and thats what fouled the spark plugs? oil in the cylinders can quickly degrade octane and cause detonation. you ever do a compression and leakdown on it before the fouled plugs?
just throwing this out there especially since you brought up milling...did you ever clay the motor? was there any piston to head contact?

 

You need big cams to run big compression, and you really should map your clearances with any build. That way there's no guessing later on if you decide to change.

 

I had not clayed the motor, and it was burning some oil. I have an AEM wideband, which typically read 12:1 to 14:1, a little under 12 on idle.

Since the Ecu was previously tuned, I'm unaware of any timing adjustments. I believe it was running bigger cams, and the shady guy I bought it off swapped them out before sale. This engine has a lot of unknown factors, and I'm at the point where it's time for a new build and want to do it right. I can post pics up tomorrow.

I'd like to stay high compression, lsv or b20v. Leaning towards a b20v. I have 3 gsr heads, 2 b18a blocks, a b20b block, and I'm running an itr trans with 4.7 lsd. Essentially from what I'm reading, to use my skunk2 pro3's, I need HIGH compression, and for that pump gas will not suffice.

 

I agree that you've probably acquired a mystery machine. The fact that you severely cracked forged pistons on an NA engine says that there was likely some heavy abuse before you ever got to it.

Don't get so hung up on static compression. The reason you need to run it up with big cams is because they lower the dynamic compression significantly by closing the intake valve later in the stroke. Start thinking of the engine as a system instead of as parts and you'll be more successful in the future. Pick your cams and build downward from there.

 

if I recall correctly a dynamic compression somewhere around 10-10.5:1 is a good number to shoot for.

 

10.5:1 is about the max you want to run. Higher than that and it's probably going to be a knock limited engine.

 

WAY to high compression for a pump gas motor! AND you killed it with a hotter plug! If anything you should've went about 2 heat ranges COLDER on plugs to help control detonation some.

Lesson learned I guess, hope you plan putting new bearings in the bottom end too, cause detonation surely killed the rod bearings.