LineC Posted July 4, 2006 Share Posted July 4, 2006 Been collecting parts for awhile now and have a quick question on this particular part of my build. I am building for 300 to 350hp max, and would also like to raise CR on my engine to as close to 8:1 as possible. I have saved for a fairly decent budget on this build but am not interested in anything past 350hp. Alright here's my question, in order to get my 8:1 CR I "think" this will work stock heights on my block and P90 head. +1mm flat tops (87mm bore) and a 2mm HKS headgasket. I guess my biggest dilemma is the HKS gasket is 91mm bore and my engine will be 87mm bore. Is this something to be concerned about? Should I try to get 8:1 CR by shaving and shimming instead of the HKS gasket? Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted July 5, 2006 Share Posted July 5, 2006 If all you are looking for is 350HP, why limit your off boost response with only 8:1 compression ratio? Assuming you are going to run an intercooler and a decent turbo, you should have no problems with the flat tops and regular head gasket.... Many people are putting turbos on NA engines with large injectors and getting that kind of power and good off boost performance as well. A little more info on your plans may help us help you.... Quote Link to comment Share on other sites More sharing options...
Pyro Posted July 5, 2006 Share Posted July 5, 2006 A L28 with dished pistons and a P90 head makes 7.4:1 cr. You need to make the combustion chamber smaller or the engine larger to make more compression. Adding a thicker head gasket is NOT how to decrease the combution chamber size. Why would you want to use a thicker head gasket then slave the head? The net effect is the same combustion chamber size. Like taking two step forward and two steps back. A L28 with dished pistons and a N47 or N42 head will make 8.3:1 cr with a stock 1mm head gasket. This is the easiest to make close to 8.0:1 cr. Quote Link to comment Share on other sites More sharing options...
LineC Posted July 5, 2006 Author Share Posted July 5, 2006 Adding a thicker head gasket is NOT how to decrease the combution chamber size. Why would you want to use a thicker head gasket then slave the head? The net effect is the same combustion chamber size. Like taking two step forward and two steps back. No no I don't want to shave and use a thicker gasket I wanted to do one or the other. I was concerned that a 91mm bore gasket would not work with a 87mm pistons. But I didn't know and that was my question. In my thinking (which might be way off) I do not want to run higher then 8:1 CR. I don't want to go wideband o2 but would I have to if I start boosting a engine around 8:3 or 8:5. Here is my plan so far but it is all subject to change, as better ideas and more searching comes in. What I have laying in boxes and such F54 not cut or bored yet, stock pistons P90 not shaved 60mm 240sx 440CC injectors with 14mm o-ring rail z31 ECU retuned (not yet though) with z32 MAF Walbro fuel pump stock exhaust manifold What I am lacking Holset HY35 turbo or p-trim t04e (I want to use Holset) New pistons (haven't decided on CR yet though) Aeromotive FPR Good intercooler Decent BOV I guess first thing I should ask is my plan on target for 300 to 350hp. I want it to be reliable and an all around fun car to drive. I plan on using a manual two stage boost control and not have the higher limit set to a piston melting limit, (already did that with my twin turbo Stealth) I will make the exhaust and downpipe after engine is in. I do not want to use the stock pistons that are in the block and have no problem boring if needed. I want to stay away from shaving the head but if I have to I will. I think my goals will let me use cast pistons or am I wrong? This is not a daily driver and I have given myself a budget of $2500 for the engine work and parts. So far I am out $300 for the parts I have so that still leaves me with what I think is plenty for machine work and the rest of my parts, (if I am over budget it wouldn't be the first time). I do not want to port and polish since I think it will be a waste of money for the power I am looking to get. Any advice on changes to my setup I honestly would greatly appreciate. Ohh and if you are a v8 fan that is not good advice to me, I am keeping the L28 Quote Link to comment Share on other sites More sharing options...
Pyro Posted July 5, 2006 Share Posted July 5, 2006 I still would recommend using stock turbo pistons with a N42 head and a stock NA cam. 8:1 cr versus 8.3:1 cr is not a huge difference. A few degrees of ignition timing reduction in 4000 rpm range and maybe a little more fuel will be the only tuning difference. A stock NA cam has 8 more degrees of intake duration as compared to a turbo cam which will bleed off some cylinder pressure and give another 500 rpms of power band You don't need a wide band to boost at 8.3:1 cr. Spend your money on a good efi system with ignition timing control. Ignition timing control is the key to prevent detonation and make great power with good mpg and drivability. Just the price of custom pistons will be 1/2 the price of a bad-A efi system. If the engine has detonation problems then turn down the timing with the EFI system or lower cylinder pressure with a little more cam. Don't spend a bunch of money on engine components if you don't have a good efi system in place first. Forget the Z31 efi. You need ignition control and easy tune changability. You could make 300hp with a completety stock L28et with T3, 15 psi of boost, a NA cam, N42 head, bar & plate IC, and a good efi system. I don't like walbro pumps. Very noisy, expensive, and are over-kill. Look at the MSD efi pump (MSD-2225) from summit racing. You can get it for only 90.00. 2500.00 will go fast, so keep the engine simple and spend the money where it counts, in the EFI system. You will also need a better clutch if you plan on using a manual transmission. Check out nipponpower.com and take a look at the stage 2 SPEC clutch. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted July 5, 2006 Share Posted July 5, 2006 You don't need a wide band to boost at 8.3:1 cr. Maybe I'm just yellow, but I want a wideband at 15psi(assuming you meant 15psi from later in the post). 2500.00 will go fast, so keep the engine simple and spend the money where it counts, in the EFI system. On a budget? I would spend $150 and put MSnS v2.2 board in it and buy the LC-1 wideband for $200 for tuning. Unless there is a particular feature you want from the name brand EFI units (I admit the feature you want may be as simple as tech support, megasquirt doesn't offer that) Quote Link to comment Share on other sites More sharing options...
Forrest Posted July 5, 2006 Share Posted July 5, 2006 Yeah, I can't imagine not having a wideband to use with a programmable EMS. It's the best 200$ you could spend. Quote Link to comment Share on other sites More sharing options...
LineC Posted July 5, 2006 Author Share Posted July 5, 2006 I have really been fighting myself about going Megasquirt, but I think I'll really need to swap over for what I want. I think my biggest fear is tuning since my prior tuning skills was turning a distributer. I am sure though this is a fear everyone has had and in no time I'll be off and tuning if I go that route. On to the cam the more I think about it I like the idea of the NA cam after reading your posts Pyro. It won't be a huge deal since I got both cams laying around but if the NA cam is closer then the stock turbo cam to the duration on the MSA stage one why not? About the n42 against the p90. I keep hearing for boosting you want the p90 since its shaped better. I know a lot of people have used the n42 but I do not want to be experiencing knock. I will not be boosting to the max on whatever the limits of my setup will be. Maybe the head is a mute point if I get the car tuned properly. Ohh ya budget is just for motor I still have money set aside for other things that need to be done like clutch, and such. I have already seen what 12 second runs will do to the stock clutch . Once again thanks for all the advice, this build will be based on information from mainly people I talk to and information from searching that I squirrel away. I am appreciate that you guys and this board are all sharing it. I'm trying to stay away from untested ideas or being a test pig to my own ideas,,,,, damn I sound chickenshit don't I? Quote Link to comment Share on other sites More sharing options...
Doug71zt Posted July 6, 2006 Share Posted July 6, 2006 Buying and tuning with a WB02 will be the cheapest power you can make. I took 3 tenths off my ET and upped my mph by almost 2 mph a couple weeks ago by logging the WB output and tuning my fuel values. The tune is still conservative, all i did was even out the mixture across the RPM range to my target AFR. If you have a good tune, a decent IC, and good gas, 300 hp is manageable on stock turbo pistons. 350 might not last - not sure but I'm close to that now. I would spend the money on good engine management and go with the N42/NA cam. You can always build the engine for more power later, and if you have a tuning problem in the beginning, no big loss if you burn a piston. I freshened a JY turbo motor and dropped it in to get my feet wet, turbo/efi-wise 5 years ago. It is still in there today with no problems. The first run down the strip was 13.7 and now I am running 12.4 on pump gas. Doug Quote Link to comment Share on other sites More sharing options...
big-phil Posted July 6, 2006 Share Posted July 6, 2006 I still would recommend using stock turbo pistons with a N42 head and a stock NA cam. 8:1 cr versus 8.3:1 cr is not a huge difference. A few degrees of ignition timing reduction in 4000 rpm range and maybe a little more fuel will be the only tuning difference. A stock NA cam has 8 more degrees of intake duration as compared to a turbo cam which will bleed off some cylinder pressure and give another 500 rpms of power band You don't need a wide band to boost at 8.3:1 cr. Spend your money on a good efi system with ignition timing control. Ignition timing control is the key to prevent detonation and make great power with good mpg and drivability. Just the price of custom pistons will be 1/2 the price of a bad-A efi system. If the engine has detonation problems then turn down the timing with the EFI system or lower cylinder pressure with a little more cam. Don't spend a bunch of money on engine components if you don't have a good efi system in place first. Forget the Z31 efi. You need ignition control and easy tune changability. You could make 300hp with a completety stock L28et with T3' date=' 15 psi of boost, a NA cam, N42 head, bar & plate IC, and a good efi system. I don't like walbro pumps. Very noisy, expensive, and are over-kill. Look at the MSD efi pump (MSD-2225) from summit racing. You can get it for only 90.00. 2500.00 will go fast, so keep the engine simple and spend the money where it counts, in the EFI system. You will also need a better clutch if you plan on using a manual transmission. Check out nipponpower.com and take a look at the stage 2 SPEC clutch.[/quote'] My n/a cam broke a while ago, and I put the cam from a p90 head I have in my n47 head, should I get another n/a cam instead of the turbo cam?? Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 6, 2006 Share Posted July 6, 2006 I have really been fighting myself about going Megasquirt' date=' but I think I'll really need to swap over for what I want. I think my biggest fear is tuning since my prior tuning skills was turning a distributer. I am sure though this is a fear everyone has had and in no time I'll be off and tuning if I go that route. [/quote'] I don't know about MSnSE but MSII is cake to program. The VE generator gets you 95% there. With a wideband go drive it around with a pasanger and tune the low load windows on the fly. I had my wife do mine on the highway, I did the street stuff. For boost, data log a run, park, adjust fuel, and log the next run. It is really easy. I would sell the Z31 ecu before you get to deep into something you can't 100% tune. Turbo pistons are alot stronger than early n/a pistons. HP is not the limit though, knock is. I have "heard" that the 79+ flat tops have the thick top ring land like the P90 turbo pistons. Maybe someone one here knows for sure. If so, using them with a P90 head and a little valve unshrouding would put you under 8.3:1. I don't know how much though. I would agree with the n/a cam, you'll want the "A" cam if you're not running a spray bar. It is ok to use a 91mm hks gasket on even a stock bore. I would run a stock gasket for what you are planning though and put the money towards something else. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted July 7, 2006 Share Posted July 7, 2006 Clifton: What car are you running MSII on, and what ignition? Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 7, 2006 Share Posted July 7, 2006 The 7m, EDIS with Supra coilpack. The L28 has SDS with standard a coil. Quote Link to comment Share on other sites More sharing options...
LineC Posted July 7, 2006 Author Share Posted July 7, 2006 Well over the last two days I have researched about 12 hours on Megasquirt and I think I have read 85% of the threads concerning this (works been slow and they got a T1 connection) and am very confident on the install and soldering and I think I am getting a lot of the tuning procedures down. Plus now I have a use for my stoneage laptop and CLio PDA if I go this route. I will definately have to spring for a WB o2 with this set up. Looks like everyone likes Megasquirt I with pcb2.2. Why is that? Price difference doesn't look like to much of an issue between pcb 2.2 and pcb3.0. Has MSnS-E came out for Megasquirt II yet? I think I am budgeting my money a lot better now and not skimping on the important stuff and spending to much on perfectly fine stuff. Still up in the air about a couple things but I have never been 100% sure on any of my engine builds. I think my next decision which luckly I don't have to make real soon is turbo. I want to be boosting around 2400 rpm but the HY35 looks like it kicks in a lot later on most peoples set up. Anyone watching this thread have strong feelings about low rpm boost vs 3600rpm boosting. Is it really that big of a deal? Quote Link to comment Share on other sites More sharing options...
mobythevan Posted July 7, 2006 Share Posted July 7, 2006 Looks like everyone likes Megasquirt I with pcb2.2 I think it is mainly because the install guide is ancient and it was written for the 2.2 pcb. MSnS_Extra is NOT available for MSII yet, so that is another reason most people will stick with MSI on either 2.2 or 3.0 pcb. But it will be available at some point. Just research and see if you really need any of the extra functions available and maybe MSII would work for you. Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 7, 2006 Share Posted July 7, 2006 I think my next decision which luckly I don't have to make real soon is turbo. I want to be boosting around 2400 rpm but the HY35 looks like it kicks in a lot later on most peoples set up. Anyone watching this thread have strong feelings about low rpm boost vs 3600rpm boosting. Is it really that big of a deal? Having a low boost threshold will hurt power. Unless you really need it to come on at 2400 rpm I would go with the HY35. 3600 rpm is still really low and will give you more rpms up top. More revs are a downshift away. It's not very often when you need to excelerate at low rpms, just like an n/a motor. I get 20 psi around 4800 rpms, depending on the gear . Quote Link to comment Share on other sites More sharing options...
Sean73 Posted July 7, 2006 Share Posted July 7, 2006 I'm running close to the same setup that you are aiming for (check sig) With flattop pistons, P90 head, and stock HG I am at 8.8:1 compression. This works fine for my current boost level of 12 psi. I'll be turning the boost up to 15 soon, and then that will be it. I thought the 8.8:1 compression was chancy, but at the same time, I did not want to alter the original "squish" design of the P90 head by increasing the HG thickness. If I could do it again, I would just suck it up and get forged pistons, and keep the CR about 8-8.5. I am using all Nissan EFI components, and it's fully programmable with my laptop and $50 EPROM programmer. If I could do it all over again, I might go with MS, since it has matured quite a bit since I built my engine. The thing I like about using the Nissan parts is that I can get it all at the junkyard, cheaply, and it works just as well. I also have a Zeitronix wideband / datalogger which has been awesome in the tuning process. Quote Link to comment Share on other sites More sharing options...
LineC Posted September 22, 2006 Author Share Posted September 22, 2006 Ok finally getting the bathroom upstairs finished and I think I will have some time for my engine build. New things have happened since I left off. I acquired all of this 2 weeks ago for a good price. (long story) 1. Turbo Engine, P90 w/HKS 2mm & Grand National Turbo, WEBER big throat TB, ECU, COMPLETE 2. Turbo Engine, P90 w/HKS 2mm (recently rebuilt) 3. Borg Warner T5 w/driveshaft 4. Borg Warner T5 w/driveshaft 5. Borg Warner T5 (broken dog ears) 6. MSA front and rear sway bars for a 280z 7. 3.9 R200 8. Gear Reduction Starter 9. 3 Core radiator 10. Misc small items 3 AFM's, 3 Turbo Dizzy's, 2 NA Dizzy w/modules, 2 sets of turbo injectors with holders So now I have plenty of parts and plan on selling off extras to help offset the cost of this build. Goal is still 300 to 350hp max. I would like to reuse the 2mmHKS gasket but still want around 8:1 cr. I want to steer away from shaving also. I think I am on the verge of needing forged flat-tops. Also still trying to locate a HY35 for less then $300 but still has some life on it. Damn these things are going for a lot on ebay lately. I have read a lot of good posts on using stock flat tops on turbo motors but the advice seems shaky. I am looking to find out if the ring lands on the flat tops and the dished are the same depth? Or if I should not even think about using stock flat tops with 8:1 compression and trying to hit 350hp. Will the flat tops hinder more then help with the P90 design? Quote Link to comment Share on other sites More sharing options...
Pyro Posted September 22, 2006 Share Posted September 22, 2006 Big-Phil, did you feel a difference between the turbo and NA cam? I feel the early 280/280zx NA cam is an improvement in high rpm power for a turbo engine. LineC, the P90 and P79 heads have better combustion chambers than the older style heads. The newer heads have a larger quenching area which is used to prevent detonation. However, this design is only effective with flat top pistons. Once a dished pistion or a thicker head gasket is used, all quenching effects are gone. So a N42 or P90 with stock dished pistons will have the same combustion chamber benifits (none). FYI, a dished L28 piston with a 2mm head gasket and N42or N47 head will make 7.94:1 cr. For quenching, there should be no more than 0.040" distance between the flat part of the combustion chamber and the top of the piston. A dish pistion can have quenching if the dish is shaped like a "D" and is not dished under the flat part of the combustion chamber. Quote Link to comment Share on other sites More sharing options...
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