Which pistons for my stroker?

[ezzzzzzz]

I've read and read and quite frankly I'm tired of searching. I'm going to build a stroker and wish for about 8.5:1 compression for use with a Eaton M62 generic supercharger. I have to following parts on hand to choose from...

 

L28ET (F54) short block

Complete LD28 engine

L20B timing cover

L24 rods, 9mm rod bolts

E88 cylinder head

P90a cylinder head (mechanical lifters)

 

I'm leaning towards the P90a because I intend to run fuel injection (SDS) but the E88 is still a contender here. The question is which rods and pistons? I would like to use the LD28 rods for better ratio but don't know what piston (if any) is compatible. The LD28 rods would be lightened to reduce mass of course. I'm guessing the KA pistons are a given for the L24 rods? I'm looking for the easiest to use (e.g. no pin bushings, surface shaving, etc. if possible). Lastly is the choice of head gasket. If the 2mm is still available through Nissan then I'd go that direction. This will be a street driven vehicle where longivity and low maintainance holds priority over max hp/tq.

Give me your flames, suggestions, recommendations and reasons.

[TheNeedForZ]

play with this. I thought everyone know about this utility already.

 

!!!too late!!!

 

choose a cam or the utility won't calculate.

 

With a P90a head(volume = P90?) + L28 crank + L24 rods + Arizona Z Car 87mm forged flat top pistons(35.37mm pin height) + 87mm bore + combustion chamber unshrouding(+1cc to chamber) +1.25mm headgasket = 8.56:1 CR with good quench.

[510six]

You could use VG30 et pistons which will stand up to higher levels of boost than an NA piston.The VG pistons have a 6mm lower pin heigth than an L series piston.

[ezzzzzzz]

The Lengine program is awesome but lacks coverage of the LD28 block and an assortment of pistons. I am leaning toward to VG piston. It seems ideal with a guesstimated c.r. of around 8.5 or 9.5 depending on using the dished or crowned design. Do these have use 21mm pin? Can both sides of the V6 be used in an L6? Where is the best source?

[TheNeedForZ]

Sometimes people asks for advice...and then not even read them. I bet 10 bucks you didn't even click on the link I gave you. The topic is beaten to death anyway, search.

[ezzzzzzz]

I'm sure that some do not read links or take suggestions. I like to think that I'm openminded enough to look at any and all advice offered. There was no link in your prior post (although I thought it was there and pointing to the Lengine program or I wouldn't have mentioned it in my post). Otherwise, I would have done so and maybe have my answer. I do search prior to asking questions. Often there is much banter about the subject and the occasional hi-jack. Sometimes there's even some hard details to work with. What you search for has an impact as well. Maybe I'm looking in the wrong areas. We need to create a sticky with the details of different combos to create a variety of displacements. Please repost that link and I'll be happy to give it a go.

[dr_hunt]

TheNeedforZ, Where is this link you so fondly talk about? Is it a dcr or scr calculator?

[TheNeedForZ]

There was no link in your prior post (although I thought it was there and pointing to the Lengine program or I wouldn't have mentioned it in my post). Otherwise, I would have done so and maybe have my answer.

 

You know that's is really weird because I don't even have the link to Lengine. I already have the Lengine program. since it's a Windows program there is no need to keep the web address after the download. TheHelix's engine utility however, needs to be run on the browser so I kept the web address.

 

Anyway, now that I have your attention, here is the link, the author is a member here as well. http://www.ozdat.com/ozdatonline/enginedesign/

 

It has a lot of parts specs including LD but no VG30E or ET specs. To get VG30E piston spec, change the spec of a VG30DE piston into 21mm pin and the rest are the same. I don't know about VG30ET specs but I don't think you need the extra dish. I thought about using VG pistons but gave up on it because it will not give good quench but rather create a condition that might be prone to detonation.

 

 

Dr.Hunt,

 

The utility is mainly for L series and other Japanese engines so I am sure you won't be interested;) But to answer your question, it is not a dcr calculator. Probably not scr either because you can change the cam specs and the calculated cr won't be effected. The link is written above.

[ezzzzzzz]

Please elaborate on your reasons for not using the VG piston.

[TheNeedForZ]

When I looked at using VG pistons, the closest I can bring them to block deck(L28) was by using a set of L24rods and LD28 crank. But that ended up with the piston 1.6mm below the deck at TDC. The headgasket is 1~1.25mm thick that means when the engine is on compression stroke there will be a 1.6+1~1.25 = 2.6~2.85mm thick of a flat region of air/fuel trapped between the combustion chamber's quench pad and piston top. Whenever there is a region of air/fuel trapped in a thin space surrounded by metal, it becomes a region that can start to knock easily. The reason for that is because flame travels to that region last and the metal surroundings act as heat sink that prevents the thin sheet of charge to burn normally. As a result, a part of air/fuel charge is preserved while temperature and pressure in the chamber elsewhere keeps on building. When condition is right the thin sheet of charge can detonate. Even when it is not knocking, the metal-charge-metal sandwich reduces power and fuel economy because flame have a hard time reaching there until burning condition improves.

 

On the other hand, if there is enough squish, the air/fuel charge becomes more turbulent to improve flame propagation and it will help surpressing detonation and allows more power to be created(more boost) before detonation emerges again.

 

The theory above was mentioned in a David Vizard book. In the book there is a comparison between a supercharged SBC with no quench and the same engine with quench after the block is decked. If you are interested I can take out excerpts and PM it to you.

[ezzzzzzz]

I'd be interested in the read. Please send the info on. It looks more like I should have a set of pistons custom made for this stroker. Any other suggestions?

[TheNeedForZ]

Here is the excerpt taken from the book "How to build & modify Chevrolet small block V-8 Cylinder heads" by David Vizard

 

 

Here he explains how squish influence detonation resistance :

 

In addition to swirl, the "squish" effect produced by the quench area can have a significant effect on how well and how rapidly the charge burns. In essence the effect of squish form the quench area is rather like that of throwing the mixture into the fire to speed the burning process......The ability to burn the charge quickly close to TDC means that less ignition advance is needed. This means more of the pressure rise can be used on the downward side of stroke rather than the tail end of the compression stroke.....As swirl and turbulence are increased, the rate of flame propagation through the charge is speeded up. This means the last part of the charge to burn spends less time exposed to the radiated heat from the flame front. This, in effect, cuts the tendency of the charge to detonate.

 

.....the closer the piston approaches the quench area, the better the squish action and the faster the charge between the piston and cylinder head deck surface is shot out into the chamber. Second, if the gap is too large it presents a "critical detonation section."

 

It appears that anytime a charge thickness of around a 0.100 in. exists, it's a prime candidate for detonation. This is especially so if it's off from the mainstream area of the combustion chamber.....On a stock Chevy a 0.038in. head gasket and a 0.050 in. deck height constitute the quench area---that is, about 0.090in. This density of charge in the quench area isn't outstandingly conductive to suppressing detonation, and often detonation will occur.

 

.....by the time these gases(air/fuel mixture) are ready to ignite, the critical charge thickness of around 0.100 in. exists; in other words, the piston has just gone past TDC and has started down the bore. These charge thicknesses are too thin to ignite and burn conventionally, but they can be burned after the effects of radiated heat and pressure from the advancing flame front do their thing. The result is detonation.

 

 

and here he shows a case example, a SC SBC improved by using quench

 

On the dyno a supercharged SBC with an 8.5:1 CR revealed trace detonation with 10psi of boost. The piston-to-deck clearance was about 0.040 in., giving a total piston-to-head clearance of 0.078in. Previous experience with other engines had indicated that the quench clearance could be significant in suppressing detonation, The engine was stripped and the block was decked 0.045in. to bring the piston 0.005 in. out of the bore, which with a Fel-Pro gsket thickness of 0.038in. gave a piston-to-head clearance of some 0.033 in.

 

The resulting CR of the assembled engine was now approx 9.0:1. No detonation was seen on 10psi of boost, and the engine made an additional 12hp under full-throttle conditions and produced better Brake Specific Fuel Consumption(BSFC) figures when delivering 60hp at 2200rpm, my standard highway cruise test. Those results were significant enough in themselves; however, subsequent tests showed that an additional 2 psi of boost could be put into the engine before detonation again reared its head. Those extra 2 psi produced some 28hp more from the engine. So in this respect we see that attention to the quench area allowed the engine to produce some 40hp more, along with a significant improvement in about-town and cruise economy.

[NZeder]

L28ET (F54) short block

Complete LD28 engine

L20B timing cover

L24 rods' date=' 9mm rod bolts

E88 cylinder head

P90a cylinder head (mechanical lifters)

[/quote']

 

hmm and I the only one who noticed this above. I might point out that a L20B timing cover will not work with the L28 (F54) block or any of the L24/26/28 blocks for that matter it is too tall. It will work with a LD28 block with minor mods so unless you are planning to use a LD28 block also you will need a standard L series timing cover ie L16/18/20a/24/26/28 the L20b cover is 19mm taller and has an extra bolt above the dizzy - if you have a copy of "How to Modify your OHC Nissan/Datsun Engine" was written by Nissan competition project engineer, Frank Honsowetz there is a picture that shows the differences.

[ezzzzzzz]

The L20B cover was acquired in case I built the LD28 block into a petrol L6.

[NZeder]

The L20B cover was acquired in case I built the LD28 block into a petrol L6.

cool that explains it then

[rayaapp2]

V07 Engine

 

 

I got my L20B cover, timing chain, and rods after the pics. I've gotta send the head off still so I didn't bother cleaning it up yet.

 

Also I have yet to do this

 

http://www.zraceproducts.com

 

 

I have a list of stuff to get still including a balancer, carrillo rods, Ross pistons, etc...

 

 

Oh almost forgot to mention:

VW standard piston size of 94mm. I let you guys play with that though it may take a while to sink in.

[NZeder]

94mm bore on a LD28 Block (227.45 high) LD28 crank, Z22E rods (149.5mm), 94mm piston with 36.45mm pin height = 3456cc with 1.8 rod/stroke (same as the L24) and 11.8:1 CR - wow big number I would guess - one question - head gasket, well make that two - taking the LD28 block out 9.5mm = hell of a lot, assume resleeve

 

EDIT: Make that three - those VW pistons you talk about these are not the ones with the 36.6 pin height and big big pin of 24mm - so assume you would go custom = right pin size, better rings to help that bady rev. You are mad...great idea

 

and one more thing - will you get the head to breath enough to handle the potential power a 3.5 could produce

[rayaapp2]

Hopefully not. I've got a spare block thanks to another local member. On top of which this is not the first attempt by anyone to go beyond 89mm. The diesel block can go to 104mm effectively making it a 4L. Problem with that is then you do have to do something about stengthening the cyinder walls. I just don't know at what point that is. The diesel walls are much thicker... because it's diesel. The specs for the diesel are not the same as the maximum bore specs for a gas engine.

 

I have already spoken to Carrillo about custom rods and to Ross about the pistons, rings, and pins. I have the L20B rods, but they aren't looking to beefy being the same size as L24 rods just much longer.

 

It's turbo'd so I'm not pushing the CR. maybe 9:1. Give me enough low end torque while the boost is coming on.

 

Custom gasket... I'm still searching. I may end up doing it the old school way with the copper rings or something.

 

I'm sending the head off to a local machinist that has been working on them since the 80's.

 

 

(My missinformation sorry)

My head will end up getting torqued to 120lbs... I beleive MY head bolts are 14mm bolts for the diesel block and the stock turbo/na petrol bolts are 12mm. That is why the cam towers must be machined. The stock ones are 10mm and the diesel ones are 12mm.

 

I've spoken with Ben and his technician at Jim Wolfe Technologies. They've been doing this long before I knew what a zcar was. Nothing new. As I said I'm not the first and some have built 4L...In fact take a good look at Jerry's car...

http://www.zraceproducts.com

I'm waiting for him to post a dyno sheet. He claims to have already made 600hp before the increase in displacement. He claims more now.

 

 

Timing control is also in the works.

 

Lots of work to do still.

 

The rod:stroke is exactly why I am using the LD block, I found out later it could be bored. I've got to start messign around with this other diesel block.

 

Pin height would be moved to 40.05mm and create a 0mm deck height. w/1mm gasket and my P90a head that's just above 9:1 if I remember right.

 

 

Anyway your squeezen my secrets out now.

[TheNeedForZ]

Just so we don't hijack this thread any furthur than we already do. Keep us updated in another thread about your personal project. I don't see the "4L" Z in the website or any other high displacement I6 Z car, it was hidden somewhere? From what I have heard from "1 fast z", who sonic tested 2 LD blocks, an LD block can only be safely overbored 2mm before requiring special liners.

http://forums.hybridz.org/showthread.php?t=107456&highlight=%22diesel+block%22