F54 + N42 + MS2 = Best settings?

[naviathan]

When increasing compression in an engine (ie putting an N42 head on an F54 N/A block) what alterations to the advance and fuel should be made? Of course after I left the states I figured out why my engine was pinging so horribly bad. 87 octane in a F54+N42 setup means big problems. Thankfully I only blew the head gasket...(again) So in preperation for going home to work on it again I'm going to pick up an MLS 2mm head gasket to drop the compression a bit. Once I get fresh fuel in the tank (92) and get ready to crank it back up, what should I be looking at to identify problems with the compression?

[Thumper]

When increasing compression in an engine (ie putting an N42 head on an F54 N/A block) what alterations to the advance and fuel should be made? Of course after I left the states I figured out why my engine was pinging so horribly bad. 87 octane in a F54+N42 setup means big problems. Thankfully I only blew the head gasket...(again) So in preperation for going home to work on it again I'm going to pick up an MLS 2mm head gasket to drop the compression a bit. Once I get fresh fuel in the tank (92) and get ready to crank it back up, what should I be looking at to identify problems with the compression?

 

I like to keep the air/fuel ratio right at 12.5:1- 13:1 depending on rpms. Then adjust timing untill you make best power. Which is usually 2-3 degrees before you start detonating. So as long as you know your a/f ratios I would slowly adjust timing untill onset of detonation in a heavy load situation (4th gear if its safe) and then back it off 2-3 degrees. But first you need to get the afr's right. Adding more fuel will cool off the cylinders alittle bit but mostly all it does is waste gas and retard the combustion. So its like you are retarding the timing. Remember the best timing map is not flat.

[olie05]

When increasing compression in an engine (ie putting an N42 head on an F54 N/A block) what alterations to the advance and fuel should be made? Of course after I left the states I figured out why my engine was pinging so horribly bad. 87 octane in a F54+N42 setup means big problems. Thankfully I only blew the head gasket...(again) So in preperation for going home to work on it again I'm going to pick up an MLS 2mm head gasket to drop the compression a bit. Once I get fresh fuel in the tank (92) and get ready to crank it back up, what should I be looking at to identify problems with the compression?

 

What cylinder blew? I had the same setup (except with n42 block), 10:1 (thereabouts) compression with a stock cam (<--thats the kicker) And I blew the gasket running full timing in a 4th gear pull on the freeway.

 

I think my total advance was in the 35-38 degree range at full throttle. Without changing anything other than the cam to a 272-282 split duration cam, I was able to floor the car without even hearing the "death rattle" The cam helps bleed off the compression.

 

Now with megasquirt I run no more than 30 degrees BTDC total, until I get my car on a wideband. I would skip the MLS gasket and go for a cam, but thats just me

 

also, another advantage to running a cam, is that you can use my map (which has been driving me around town everyday for about 4 months) as a starting point, or at least a reference point.

[Thumper]

Olie, Are you running stock injectors? If so i'm going to steal your tune this wknd to get my car running.

[Zmanco]

I'm with Olie05 in that a more aggressive cam will lower the effective CR some. However, my own experience with max advance is that I'm limited to the low 30 degree range before I can hear detonation (flat top pistons .030" over, N42 head, 284 degrees and .480" lift Delta Cams regrind).

 

I remember a thread where BRAAP said that he would rather see the CR lowered in order to run the full (~35 degrees) advance. Perhaps he will see this and weigh in on this again if my memory isn't quite right.

[naviathan]

What cylinder blew? I had the same setup (except with n42 block), 10:1 (thereabouts) compression with a stock cam (<--thats the kicker) And I blew the gasket running full timing in a 4th gear pull on the freeway.

 

I think my total advance was in the 35-38 degree range at full throttle. Without changing anything other than the cam to a 272-282 split duration cam, I was able to floor the car without even hearing the "death rattle" The cam helps bleed off the compression.

 

Now with megasquirt I run no more than 30 degrees BTDC total, until I get my car on a wideband. I would skip the MLS gasket and go for a cam, but thats just me

 

also, another advantage to running a cam, is that you can use my map (which has been driving me around town everyday for about 4 months) as a starting point, or at least a reference point.

It blew number 5. Coolant was just pouring into the cylinder.

[z-ya]

I have a good fuel only N47-F54-NA base map for turbo injectors if anyone is interested.

 

Run a stock Nissan head gasket. If you run a metal one, and continue to have detonation problems, you will be replacing more than the head gasket. The head gasket is a good safely fuse. Hear is what happen to my SC motor with a metal gasket and detonation:

 

http://forums.hybridz.org/showthread.php?t=128000

 

Plus why lower the compression ratio. You just need to spend some time tuning to get the advance and AFR right.

 

On high comp NA L6 motors I've tuned them around 13:1 AFR, with 25-28deg max advance. This will produce good power (180WHP on my last build) on northeast 93 octane pump gas.