Newbie L30ET Build

[EvilC]

Pete,

 

Makes sense what you are saying. I do need to double check the pin height - believe it is wrong. In a twist of events, I can't track down a P90 head local to me...go figure! If I had one, I would just assemble the engine that way and be done.

[z-ya]

Pete,

 

Makes sense what you are saying. I do need to double check the pin height - believe it is wrong. In a twist of events, I can't track down a P90 head local to me...go figure! If I had one, I would just assemble the engine that way and be done.

 

You can also just measure the deck height since it is already assembled. Yo need a dial indicator. I have a couple P90A heads if you want to do the conversion to solid lifters (or run hydraulic). I run a hydraulic head in my turbo Z. Makes 300WHP @ 15psi. Stock long block. the other option is P79. You got all winter to find a P90, right?

[rags]

Pete\Clive,

 

The pistons are 1mm down in the hole. I can't remember the exact pin height but I do know whatever it is, the piston is 1mm below deck height. I know because this was what I ordered and did all of the measuring 45 times This post will undoubtedly start the "the pistons are built wrong, you have no quench, etc, etc". Been there, done that. In any event, they are 1mm below deck so with a 1mm gasket, you'll be closer to 9.7-1 comp ratio with an E88.

 

Joe

[EvilC]

As promised for the newbies like me, I wil clear up the info as I understand it and post pictures!

 

Yeah Pete, I have all winter but would like to track one down sooner than later to get this thing going, if not spring will be here and track days start again for the red Z, lol.

[z-ya]

Pete\Clive,

 

The pistons are 1mm down in the hole. I can't remember the exact pin height but I do know whatever it is, the piston is 1mm below deck height. I know because this was what I ordered and did all of the measuring 45 times This post will undoubtedly start the "the pistons are built wrong, you have no quench, etc, etc". Been there, done that. In any event, they are 1mm below deck so with a 1mm gasket, you'll be closer to 9.7-1 comp ratio with an E88.

 

Joe

 

Read about quench and squish enough on this forum. I'm not goin' there.

 

Even with them 1mm in the hole, it is probably still worth checking the valve to piston clearance (depending on what cam you are running).

[rags]

Pete,

 

I built 3 engines using these pistons. 1 with an E31 for a NA 3 liter with Webers and 2 turbo motors using a P90 which yielded 8.5-1 comp ration. You've seen to yellow car run which is one of the turbo motors. No problems with piston to valve clearance when using stock cams which I believe Clive will be using.

 

Should be a nice NA motor as well as a nice turbo motor

[EvilC]

Cylinder head quench area- what is it and what does it look like? Why is it needed?

 

Quench or squish area is typically the flat area on the top of the piston that's almost level with the top of the block deck. It must have a corresponding flat area on the deck surface of the head to qualify as quench area.

This picture here is the best visual representation for me:

 

If you look at a combustion chamber, you will usually see these flat areas, and they will have the volume of the actual combustion chamber between them. When the piston is compressing the mixture, as the piston nears the head, the flat areas on the head and piston come together and force the mixture from those areas to "squish" into the chamber, where the spark plug and burning mixture reside, so you achieve a more complete burn.

 

Here is a stock E88 head:

Here is a stock P90 head:

 

Comparing the two heads above, you can see the flat area of the p90 head to help achieve the quench or “squirting†into the area needed. The e88 head has a round chamber with no quench area and doesn’t help with this turbo application. The quench area also runs cooler than the rest of the chamber / piston. These lower temperatures are where the “quench†comes from and make sense when you think about the term “quench your thirstâ€.

 

When properly designed, the quench areas can have a tremendous effect on the quality of combustion, and allow higher compression ratios.

 

Here is a good read on related issues:

http://www.davidandjemma.com/mazda/FAQ/quench.htm

Another engine building tool: http://www.ozdat.com/ozdatonline/enginedesign/

[z-ya]

Since this has been covered to very painful extremes in other threads, my only comment would be with this picture:

 

 

Usually you would want a positive deck height (piston protruding above deck surface)so that the piston to head clearance is minimal (taking into consideration rod and piston stretch at high RPMs).

 

On my recent build you can see that the piston is about 0.004" (0.1mm) above the deck. The object is to get the piston as close to the head as possible to improve the squish.

 

[EvilC]

Pete I hear you. I have been doing lots and lots of reading trying to tie in all the points for it to make sense to me. As you can see, I am going off of a piston design Joe was already running.

 

So back to the newbie info and how quench area ties in two forms of failure and how/why head/piston/timing is all related:

 

So we start here review of “normal combustionâ€-

 

It is the burning of a fuel and air mixture charge in the combustion chamber. It should burn in a steady, even fashion across the chamber, originating at the spark plug and progressing across the chamber in a three dimensional fashion. Similar to a pebble in a glass smooth pond with the ripples spreading out, the flame front should progress in an orderly fashion. The burn moves all the way across the chamber and quenches (cools) against the walls and the piston crown. The burn should be complete with no remaining fuel-air mixture. Note that the mixture does not "explode" but burns in an orderly fashion.

 

Detonation:

Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug.

 

Detonation causes a very high, very sharp pressure spike in the combustion chamber but it is of a very short duration. If you look at a pressure trace of the combustion chamber process, you would see the normal burn as a normal pressure rise, and then all of a sudden you would see a very sharp spike when the detonation occurred. That spike always occurs after the spark plug fires. The sharp spike in pressure creates a force in the combustion chamber. It causes the structure of the engine to ring, or resonate, much as if it were hit by a hammer. This noise or vibration is what a knock sensor picks up.

 

Detonation causes three types of failure:

 

1. Mechanical damage (broken ring lands)

2. Abrasion (pitting of the piston crown)*

3. Overheating (scuffed piston skirts due to excess heat input or high coolant temperatures)

 

 

*Another thing detonation can cause is a sandblasted appearance to the top of the piston. The piston near the perimeter will typically have that kind of look if detonation occurs. It is a swiss-cheesy look on a microscopic basis. The detonation, the mechanical pounding, actually mechanically erodes or fatigues material out of the piston. You can typically expect to see that sanded look in the part of the chamber most distant from the spark plug, because if you think about it, you would ignite the flame front at the plug, it would travel across the chamber before it got to the farthest reaches of the chamber where the end gas spontaneously combusted. That's where you will see the effects of the detonation; you might see it at the hottest part of the chamber in some engines, possibly by the exhaust valves. In that case the end gas was heated to detonation by the residual heat in the valve.

 

FACT

 

Engines that are detonating will tend to overheat, because the boundary layer of gas gets interrupted against the cylinder head and heat gets transferred from the combustion chamber into the cylinder head and into the coolant. So it starts to overheat. The more it overheats, the hotter the engine, the hotter the end gas, the more it wants to detonate, the more it wants to overheat. It's a snowball effect. That's why an overheating engine wants to detonate and that's why engine detonation tends to cause overheating.

 

 

 

 

Pre-ignition:

Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. With pre-ignition, the ignition of the charge happens far ahead of the spark plug firing in the compression. There is no very rapid pressure spike like with detonation. Instead, it is a tremendous amount of pressure which is present for a very long dwell time, i.e., the entire compression stroke. That's what puts such large loads on the parts. There is no sharp pressure spike to resonate the block and the head to cause any noise. So you never hear it, the engine just blows up! That's why pre-ignition is so insidious. It is hardly detectable before it occurs. When it occurs you only know about it after the fact. It causes a catastrophic failure very quickly because the heat and pressures are so intense. The engine just blows up!

 

Octane rating or octane number is a standard measure of the anti-knock properties (i.e. the performance) of a motor fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high-compression engines that generally have higher performance. This is why you hear a pinging sound when you use 87 in an engine that is rated to use 93 and lack power when you are going by the feel of the pants.

 

 

I will address timing and such at length later in this thread as I understand it.

 

 

So with this information, it is clear to see why the p90 head would be ideal for turbo application based on its compression characteristics and chamber design. Proper head work would only increase the efficiency of the head and help prolong the life of the engine along with proper tuning.

 

Here is a good read: http://www.streetrodstuff.com/Articles/Engine/Detonation/index.php

[blueshark123]

Engine break-in period is a myth. Break that bad boy in on a dyno and you're good to go. I broke my built k20 in on the dyno on first start-up. Did a leakdown a few weeks later and the numbers were perfect.

Edited November 30, 2011 by blueshark123

[EvilC]

Engine break-in period is a myth. Break that bad boy in on a dyno and you're good to go. I broke my built k20 in on the dyno on first start-up. Did a leakdown a few weeks later and the numbers were perfect.

 

 

Well I don't think you "broke" yours on the dyno on first start-up

 

How long were the engine dyno runs?

Edited November 30, 2011 by EvilC

[z-ya]

Engine break-in period is a myth. Break that bad boy in on a dyno and you're good to go. I broke my built k20 in on the dyno on first start-up. Did a leakdown a few weeks later and the numbers were perfect.

 

Maybe new engines, but not when it comes to an L series engine. Especially when using a high lift cam and heavy duty springs. Get as much oil on the cam during break in as possible. Use a high zinc and phosphorus break in additive or oil. This also helps with bearing break in.

[rags]

Correct me if I'm wrong Clive, but aren't you breaking in the motor with a stock E88 and cam? If you can't find a decent P90 to work with I have a virgin one I've been saving for who knows what that I might be willing to let you pry out of my hands. Gonna cost you big time though

[EvilC]

I was planning on doing that since the L26 is running great but if you have one I can cough up the money for then I will just wait and do it once like Pete advised. I just have to pay up some debt someone else caused me so for now throw it on my tab!

 

 

Here is a real newbie question......I know the answer but here we go:

 

How long is the break in process and is it true you should run the car at various rpms for proper break in? Is there a physical change you can see, example - smoke color from the tail pipe?

Edited November 30, 2011 by EvilC

[blueshark123]

Well I don't think you "broke" yours on the dyno on first start-up

 

How long were the engine dyno runs?

 

The tuner took about 30-45 mins to break it in. Ran it through different rpms and different loads

[z-ya]

Here is a real newbie question......I know the answer but here we go:

How long is the break in process and is it true you should run the car at various rpms for proper break in? Is there a physical change you can see, example - smoke color from the tail pipe?

 

I think the most important thing is to keep the RPMs above 2000 so that there is plenty of oil getting to cam and rocker arms. Don't let it idle much for the first 5-10 minutes of running.

 

Valvoline VR is a good break in oil because it contains zinc and phosphorus. And since it is relatively inexpensive, you don't feel all that bad draining it after the first hour or so of running. Add some Redline break in additive along with the Valvoline VR.

[EvilC]

Small update:

 

I was able to pick up a p90 head from Joe (rags) and dropped it off at the local machine shop. Also picked up a 38mm WG and still tracking down a 240sx TB with sensor. I already have the Arizona Z adaptor for the TB to the intake manni. Waiting for the fuel rail to come in and will mock it all up before I send the intake out for a clean up and powdercoat.

[rossman]

I have a 240sx TB W/TPS that I'll let go real cheep. Let me know.

[Gollum]

I know you just bought the head, but I'd personally pass on the P90 with the slugs down 1mm in the hole. Not that it'll be a "bad" combo, it's just not going to be using the quench area. So in essence you could just as easily run any other L head you wanted providing it reaches a compression ratio you're happy with for you application.

 

If you just want the P90 for an easy turbo setup then sure, run it. I don't think it'll be "bad". Just don't be believing you're taking advantage of the chamber shape.

 

The reason why the clearance has to be so tight can be seen on a large scale in your own home. If your bathroom is a small enough room with tight sealed windows then when you go to open the door you can feel the resistance as you open the door because of the air wanting to equalize. When you go to close the door you get the same thing. Close the door fast enough and you feel a resistance at the very end. At the very end air stops moving freely and you've started squishing the air into the bathroom. Until that air gap in the door gets fairly small the air moves however it wants. Get it very close to closed and all of the sudden the air becomes much more "solid", or more of a liquid than a gas.

 

The same happens in your chamber. If that gap doesn't close down small enough the air doesn't get "pushed" and moved around very much, and that's the point. You have to remember that as you're compressing that air it's becoming much thicker in a sense, and thus the air is going to have much more resistance and start acting more and more like a fluid than a gas (realize I mean this in a conceptual sense for our minds, not a literal physics sense). To simplify it a bit, running a quench pad with a large clearance is like mixing your gas charge like jello with a spoon, but getting that tolerance tight is like hitting a balloon with a baseball bat. The level of effectiveness changes dramatically.

 

Now, getting into semantics we can argue that compression level and stroke length, quench pad size, etc will all effect how close you really need to get to make an impact. Problem with all that though, is that we already know how built L motors have performed and we know that most builders are hunting for sub .3mm clearances.

[chuckles]

just subscribing. Nice write up!