L28 shaved and valve timing question

[280z"Vador"]

I've got my l28et rebuilt 2 years ago and since then, trying to make the engine run like a charm.

 

I've done pretty good improvements with my megasquirt setup since then, and few things on the engine but I'm not feeling that the engine is still ok :S

 

What I know for sure is that the engine ping easily and when I think the ping is gone, I'm just feeling that my timing is too retarded (no top end but good feeling of torq in low rev and full boost, 10psi, near 2800rpm) I need to take off 2 degrees per PSI in my megasquirt if I want to run it "ok".

 

So my question is:

My head is shaved to the maximum of what the Datsun mechanical book says. I'm runing no shim on my cam tower. If my valve timing was off just a bit, what would be the symptoms?

 

Since my timing is done by the book, can I try an other slot if I'm slightly off just to see if any improvement?

 

 

Don't missread, my engine is running fine since those 2 years but I can't get my engine runing fine for a track session for exemple OR just not being affraid to push it at 5500rpm when I want. And I just want to know the symptoms of a cam gear slightly off.

 

My setup:

L28et

MSII

Stock t3

3in downpipe

280z distr.

FMIC

trying to make it run great a 10psi and 14psi

stock 270cc injectors (440cc soon)

adjustable FPR

 

Thanks!

Edited August 15, 2012 by 280z"Vador"

[calpoly-z]

I don't have an answer for your question exactly but I would recommend picking up some cam tower shims to equal the amount of material removed from the head. My head is only shaved 20-30 thou and the machine sop that did the work highly recommended the use of shims. They are not expensive and any machine shop should be able to order them for you. I am fairly sure that just changing your sprocket position to 2 or 3 will not alleviate your issue, though I could be mistaken.

[280z"Vador"]

Well, the problem (if there's any) is not necessary from there but I just want to clear this point and make sure it is something else. I'm just pretty sure that an L28et can run better... If shims are needed, I will put somes and that's why I want to know the symptoms of a car that barely need shims

[Zmanco]

I think there are two issues:

 

1) Usually when a head is shaved, cam towers are added to maintain the same length between the cam and crank gears. There is a tension adjustor for the timing chain, but it has a limited range it can adjust. You didn't say how much the head is shaved, but I'll guess it's much less than the .080" that most do when they're looking to bump up the compression. The fact that you've run it for 2 years suggests that you can get away without adding shims.

 

2) Shaving the head without adding shims to the towers will affect cam timing by retarding it. This will typically shift the power peak to a higher RPM range. You'll notice the difference by feeling less torque at low revs and then the engine will surge as the revs build. Ok, that's an exaggeration, but that's the general affect. If you want to experiment with cam timing, get an adjustable cam gear and make small changes and see which combination gives you the balance between low end torque and high end power that you like. I'd argue this is a personal preference so try a few combinations and then settle on the one you like best.

 

Keep in mind that if you're still running the stock turbo and cam and are pulling 2 deg timing for every lb of boost, it's not surprising that you aren't making much power after 5500 rpm. If you want an engine that does, you'll need a cam with more lift and overlap, and depending on how much more power you're seeking, a bigger turbo. In short, there's a good chance that you're near the limit of what you can get out of the setup you have. Putting it on a dyno would be a small investment that would show you just where you are.

[280z"Vador"]

Wow thanks a lot! This is exactly what I wanted to ear. I did a dyno run a year ago, my tuning wasn't top notch but I made 230rwhp and 290lbs of torq at 10-11psi. I'm planning putting a A cam this winter anyway.

 

Yea my head is not shaved by a lot, it wasn't for a compression bump but just to put it straight.

 

Thanks for the answer! I will look foward for a leak somewhere. I'm really near to get what I want anyway , just wanted to be sure to put effort on the right things to make it ready for the track Always hard to tell and compare the feeling of an other L28et here in Quebec

I think there are two issues:

 

1) Usually when a head is shaved, cam towers are added to maintain the same length between the cam and crank gears. There is a tension adjustor for the timing chain, but it has a limited range it can adjust. You didn't say how much the head is shaved, but I'll guess it's much less than the .080" that most do when they're looking to bump up the compression. The fact that you've run it for 2 years suggests that you can get away without adding shims.

 

2) Shaving the head without adding shims to the towers will affect cam timing by retarding it. This will typically shift the power peak to a higher RPM range. You'll notice the difference by feeling less torque at low revs and then the engine will surge as the revs build. Ok, that's an exaggeration, but that's the general affect. If you want to experiment with cam timing, get an adjustable cam gear and make small changes and see which combination gives you the balance between low end torque and high end power that you like. I'd argue this is a personal preference so try a few combinations and then settle on the one you like best.

 

Keep in mind that if you're still running the stock turbo and cam and are pulling 2 deg timing for every lb of boost, it's not surprising that you aren't making much power after 5500 rpm. If you want an engine that does, you'll need a cam with more lift and overlap, and depending on how much more power you're seeking, a bigger turbo. In short, there's a good chance that you're near the limit of what you can get out of the setup you have. Putting it on a dyno would be a small investment that would show you just where you are.

[NewZed]

 

I've done pretty good improvements with my megasquirt setup since then,

 

What I know for sure is that the engine ping easily and when I think the ping is gone,

 

I need to take off 2 degrees per PSI in my megasquirt if I want to run it "ok".

 

 

My head is shaved to the maximum of what the Datsun mechanical book says.

 

Since my timing is done by the book,

 

My setup:

L28et

MSII

 

280z distr.

FMIC

 

trying to make it run great a 10psi and 14psi

stock 270cc injectors (440cc soon)

adjustable FPR

 

Thanks!

 

Just curious and trying to learn something new. I see some things in your setup that don't seem to fit the average MS II setup and have a few questons.

 

What Nissan mechanical book are you using and what is the number for the maximum that it says you can shave?

 

Is it the stock P90 or P90A head?

 

Have you calculated the compression ratio?

 

Why are you using a 280Z distributor? Is it locked? Do you still have a CAS somewhere?

 

What, exactly, are the timing numbers - initial, advance curves, etc.? If you're using MS II for timing, timing "by the book" doesn't really mean much, unless you're just talking about the static timing.

 

Plus the basic stuff like type of gas being used and if this is for the track or for street.

 

Also, seems like if you could supply AFR and timing curves, they would help out to use for feedback.

 

As I said, just trying to learn something myself. You might be focusing on the wrong thing.

[280z"Vador"]

Just curious and trying to learn something new. I see some things in your setup that don't seem to fit the average MS II setup and have a few questons.

 

What Nissan mechanical book are you using and what is the number for the maximum that it says you can shave?

 

DATSUN original FSM, Block + head maximum is 0,0079

 

Is it the stock P90 or P90A head?

 

P90 with a N42 block

 

Have you calculated the compression ratio?

 

No because i'm supposed to be in the "ok" nissan zone but probably the compression is a bit more than stock since the head is shaved but I don't think it can change that much. For the 2-1.5 degree per PSI, I don't think I can use numbers from others anyway, I'm tuning until there is no ping, so if I have a bit more compression, I understand that my timing setup gonna be lower

 

Why are you using a 280Z distributor? Is it locked? Do you still have a CAS somewhere?

 

Locked, I'm using a 280z distributor because my original setup was from a N42/N42 with all the stuff from a L28et. I'm now using a P90 head with my old N42 block. I'm planning to put a 280ZX distributor but I need a turbo shaft (I have the distributor)

 

What, exactly, are the timing numbers - initial, advance curves, etc.? If you're using MS II for timing, timing "by the book" doesn't really mean much, unless you're just talking about the static timing.

 

I was talking about the valve timing, so slot 2 on the cam gear. All my timing is rebuilt (new chain, tensionner, etc) and correctly done. My ignition timing (mechanical) is set to 0 so I can use the megasquirt properly.

 

Plus the basic stuff like type of gas being used and if this is for the track or for street.

 

91 octan without ethanol. This is my summer car but I'm planning to take it on the track few times

 

Also, seems like if you could supply AFR and timing curves, they would help out to use for feedback.

 

Yes sure, I'm going to post that later I can put my MS file if you want to look at everything too! Like I said, my engine is runing really fine when's cold of when I'm runing. When I stop, it takes few minutes of runing before it is runing fine again. When conditions are perfect, the car is runing pretty well! Like I said, I don't think the valve timing is the problem but I was curious of the symptoms. It's really not that bad, I can pull hard and have fun with my car, and with my actual settings, it doesn't ping, I think it's more of a megasquirt overall setting problem. For the rest, maybe that's just the shitty turbo cam that makes this floating feeling at high RPM[/u][/b]

 

As I said, just trying to learn something myself. You might be focusing on the wrong thing.

 

And I appreciate your help!

Edited August 15, 2012 by 280z"Vador"

[280z"Vador"]

 

 

To DL the MSQ: http://www.2shared.com/file/ES05NLDz/15-08-2012.html

[dexter72]

What are your afr's ?.

 

I am thinking along the lines that the stock injectors are close to there max.

 

Also I have read that trying to run more than 12psi of boost from a stock T-3 is not a good idea, Just pumping more heat.

[280z"Vador"]

What are your afr's ?.

 

I am thinking along the lines that the stock injectors are close to there max.

 

Also I have read that trying to run more than 12psi of boost from a stock T-3 is not a good idea, Just pumping more heat.

 

11.5 at woot (10psi). My fuel pressure is pumped a bit so I can provide more fuel but I know that 14psi is the top max with like 60psi in the rail. I'm actually not running at 14psi, I'm 10psi for now and I don't want to run 14psi all the time anyway, 10 is enough for having fun 14psi is nice but you know, it's just for some pull. If I'm going to the track, I will run 10psi for sure. GT35 gonna wait until the end of my university

 

When I'll have the time, I'm gonna put my 440cc for sure... I don't like running the injectors on the edge :S

Edited August 16, 2012 by 280z"Vador"

[280z"Vador"]

Problem Fixed It was an error in my tune causing the AFR map to battle with the VE map even if the open/closed loop was set. The car is now reving perfectly! I'm sooo happy