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L28 N42/N42 NEED HELP CHOOSING TURBO!

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So you may have seen my build thread. I am converting my N/A L28 to turbo using the stock N42/N42 motor with a 2mm HKS head gasket and a compression ratio of 7.65:1. Upon my research I have found that finding the exact turbo for this build is alot harder than I though. And requires some pretty good knowledge of how turbos work, compressor maps etc.. I've done some searching here and there but havent seen anyone doing my setup so far with the N42 combo with the 2mm gasket. Feel free to chime in and I'm curios to know what turbos you guys are running, and also if you have some helpful advice to steer me in the right direction that would be very helpful as well. I will continue my research either way. 

Here is what my goals are:

Full spool by 3k-4k rpms. 

300whp capable. 

500-900 dollar price range (preferably around 700-800 if possible)

These are the things I can think of at the moment, I am probably forgetting something. 

but a 3-4k spool seems like the best for the rpm range of this build (6500).

Feel free to chime in with any advice, criticism, or whatever you'd like! I am wanting to learn, and wanting to make sure my setup is right the first time. Like I said earlier I will continue this research but I figured I'd put this post out here so I can see what people have to say. 

 

Shameless build plug >Click Me< 

 

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A basic T3-T40 50 Trim with .63 AR will work just dandy.

Note on head gasket. No need to drop compression that low.  Too low of compression will turn the car into a Dog. I think we discussed this in another thread. Or was that someone else??

Edit: It was someone else. Zeiss150. But you may want to check out his thread. http://forums.hybridz.org/topic/128138-low-compression/

Is your engine the N42 with Flat Tops and P90 head?  If so use the stock thickness head gasket. OEM Nissan gasket is good. ARP head studs.  A good intercooler ( Look at Treadstone ) 93 pump gas.  You actually want CR in the 8.5 range. Nissan was far too conservative on that motor. Lack of intercooler was one reason. If you can't get 93 or 94 Octane fuel, look into adding Water/Meth injection. 

Lots of local 510 Turbo guys running 10 to 15 lbs boost on L -series engines with CR from 9.0 all the way up to 10.5 CR with 16 lbs Boost. Last example is a HEAVILY modified engine that Dyno's 300 RWHP out of a 2.1 liter L20B on VP C16.  ( We don't have much access to E85 in BC ). On the street with 93 Octane he runs 10-12 PSI Boost. Big intercooler, lots of  H2O/Meth injection and a very, very well built engine ( By Specialty engineering ) . Oh yeah. And the fellow ( Keith law ) is old school. So he runs it with a custom built  WEber downdraft in a custom blow through application. He's been running this combo for over 30 years now... 

turbocharging_005.jpg

 

 

Edited by Chickenman

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Sorry, had your build mixed up with Zeiss 150. You would be better off with a P90 head and the N42 block IMHO. Does your N42 block have dished pistons or Flat Tops?  That makes a big difference to the CR. CR between 8.0 to 8.5 will be fine with a P90 head.

The N42 head is  too prone to detonation, unless your weld up the combustion chamber. And that's a big job. The the N42 is more of a NA head.  The P90 is much better for a Turbo motor. Better quench than N42/N47 as well. BTW, adding a thicker head gasket actually makes quench worse, and can increase detonation. So you might want to re-think that. 

My recommendation is to build two short blocks. One with a Mule engine. Stock short block with dished pistons. Build it decent.,  but don't put a ton of money into it, Basically just freshen up a good used short block. This is your sacrificial Lamb for when things go Chernobyl.  And they will... at some point. Melt down the cheap motor while you are learning how to Tune a Turbo. Once you have the Tune and Boost levels sorted... then put in the Big $$$ short block. 

Local Road Racer made 400 hp on a stock short block with Cast pistons. T3/T4 at 15 lbs boost. Engine lasted 3 seasons of Road Racing till he broke a  Stock Piston ( Ring lands ) . He was expecting half a season. He actually started cranking up the boost higher and higher , because he wanted to put the new $$$ short block in... but the old Mule engine wouldn't die!!

 

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On injectors, I would recommend going with 550's. This will give you room for expansion. At some point you will be bitten by the Boost bug and are going to run out of injector with the 440's. The 550's are not crazy big and will idle nicely with a standalone ECU controlling things. 

Using the following calculator, you will see that 360 Crank HP ( 300 WHP using 20% loss ) with a BSFC of .60 ( Typical Turbo value ) and 80% duty cycle ( what you should be aiming for ) requires 476 cc/min Injectors. So your 440's may already be too small for your goals. Better to be a bit too big with injectors than too small. 

https://www.rceng.com/technical.aspx

Injector sizing ScreenShot002.jpg

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2 hours ago, Chickenman said:

Sorry, had your build mixed up with Zeiss 150. You would be better off with a P90 head and the N42 block IMHO. Does your N42 block have dished pistons or Flat Tops?  That makes a big difference to the CR. CR between 8.0 to 8.5 will be fine with a P90 head.

The N42 head is  too prone to detonation, unless your weld up the combustion chamber. And that's a big job. The the N42 is more of a NA head.  The P90 is much better for a Turbo motor. Better quench than N42/N47 as well. BTW, adding a thicker head gasket actually makes quench worse, and can increase detonation. So you might want to re-think that. 

My recommendation is to build two short blocks. One with a Mule engine. Stock short block with dished pistons. Build it decent.,  but don't put a ton of money into it, Basically just freshen up a good used short block. This is your sacrificial Lamb for when things go Chernobyl.  And they will... at some point. Melt down the cheap motor while you are learning how to Tune a Turbo. Once you have the Tune and Boost levels sorted... then put in the Big $$$ short block. 

Local Road Racer made 400 hp on a stock short block with Cast pistons. T3/T4 at 15 lbs boost. Engine lasted 3 seasons of Road Racing till he broke a  Stock Piston ( Ring lands ) . He was expecting half a season. He actually started cranking up the boost higher and higher , because he wanted to put the new $$$ short block in... but the old Mule engine wouldn't die!!

 

Interesting.. My build is based off of another member that successfully ran a turbo on his stock n42 head and block. (bonfire79 on zcar.com).

My setup is n42 head and block with dished pistons. The current compression ratio is 8.21:1. 

This is the guide I have been following: http://www.zcar.com/forum/10-70-83-tech-discussion-forum/376338-how-convert-n-l28-turbo.html

As for tuning I am having it professionally tuned. But I definitely see your point on being cautious ( I certainly dont want it to blow up)

And these motors really seem to be mules! That's impressive to say the least about the 400hp motor on a stock bottom end.  I'll definitely up the injectors if that's the case as well. Wouldn't want to fall short on fuel.

Also where I live in CA we only have 91 at the most, which sucks! Will I 100% need a water/meth system for this to operate safely?  

Edit: A P90 head would drop my compression ratio to 7.5:1, even lower than my original target, what other heads work well with turbos?

Edited by RefreshRate

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Your combo is actually fairly popular for turbo swaps, especially in countries that didn't get the L28ET. I know I've considered it too, I have the same block/head in my 76. You mentioned in your build that you joined some facebook groups for datsun stuff, are you part of "Church of L Series"? Unlike DPAN or some other parts groups, "the Church" as they sort of jokingly call it is strictly L engines and a lot of really knowledgeable guys frequent the page, even Tony D who you've seen here. Would be a good one to join if you're trying to get even more info from more sources. 

Biggest issue with making more power for the turbo engines was the J pipe and now primitive EFI controls. The efi definitely works well if you know what you're doing, but you can't really modify it. Running custom EFI and an intercooler are your biggest steps for boosting safely. Water or methanol are definitely not required for 300, at least not based on any builds I've seen. To make 300 in the 4 cylinder L20? Yes... but we have two extra cylinders and have less issues making that kind of power. 

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7 minutes ago, Zetsaz said:

Your combo is actually fairly popular for turbo swaps, especially in countries that didn't get the L28ET. I know I've considered it too, I have the same block/head in my 76. You mentioned in your build that you joined some facebook groups for datsun stuff, are you part of "Church of L Series"? Unlike DPAN or some other parts groups, "the Church" as they sort of jokingly call it is strictly L engines and a lot of really knowledgeable guys frequent the page, even Tony D who you've seen here. Would be a good one to join if you're trying to get even more info from more sources. 

Biggest issue with making more power for the turbo engines was the J pipe and now primitive EFI controls. The efi definitely works well if you know what you're doing, but you can't really modify it. Running custom EFI and an intercooler are your biggest steps for boosting safely. Water or methanol are definitely not required for 300, at least not based on any builds I've seen. To make 300 in the 4 cylinder L20? Yes... but we have two extra cylinders and have less issues making that kind of power. 

That is what I've read, and one of the reasons I started down this road. And I am apart of the "Church" lol. I have asked some questions regarding this build today to see what I get as a response. 

And as for EFI I am having a full new EFI harness built for the build using Megasquirt.  And definitely running an intercooler and all that good stuff. >click here to see my build thread<

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3 hours ago, RefreshRate said:

Interesting.. My build is based off of another member that successfully ran a turbo on his stock n42 head and block. (bonfire79 on zcar.com).

My setup is n42 head and block with dished pistons. The current compression ratio is 8.21:1. 

This is the guide I have been following: http://www.zcar.com/forum/10-70-83-tech-discussion-forum/376338-how-convert-n-l28-turbo.html

As for tuning I am having it professionally tuned. But I definitely see your point on being cautious ( I certainly dont want it to blow up)

And these motors really seem to be mules! That's impressive to say the least about the 400hp motor on a stock bottom end.  I'll definitely up the injectors if that's the case as well. Wouldn't want to fall short on fuel.

Also where I live in CA we only have 91 at the most, which sucks! Will I 100% need a water/meth system for this to operate safely?  

Edit: A P90 head would drop my compression ratio to 7.5:1, even lower than my original target, what other heads work well with turbos?

The P90 head with Flat Top pistons would have been ideal.  The P90 with dished pistons is the stock 

The P90 head with dished pistons still has an advantage over the N42 head. The combustion shape of the P90 has a better quench area. Quench area creates turbulence in the mixture and helps prevent detonation. That is critical on a Turbo motor.  When you add a thicker head gasket, you reduce quench... so you can actually end up with an engine being more detonation by reducing the compression ratio that way. Especially if you have an engine with a head design that is prone to detonation... like the N42 and N47 are.

Not saying that you can't make an N42/N47 combo work... but it will be less than optimal. And for crappy California 91 Octane fuel, I would definitely run H20/Meth injection as a fail safe with an N42 head. That's just my personal opinion mind you. 

Either way with a good intercooler and proper engine management you can run a higher compression ratio than what Nissan did back in the day. Programmable ignition timing and programmable fuel curves will go a long way on controlling detonation. 

BTW, I have a NA F54 Flat top with N47 heads and 10.3 to 1 CR. I have to be careful with ignition timing on that with 91 Octane.  Stock(ish ) distributor at this point. 

 

 

Edited by Chickenman

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2 hours ago, Chickenman said:

The P90 head with Flat Top pistons would have been ideal.  The P90 with dished pistons is the stock 

The P90 head with dished pistons still has an advantage over the N42 head. The combustion shape of the P90 has a better quench area. Quench area creates turbulence in the mixture and helps prevent detonation. That is critical on a Turbo motor.  When you add a thicker head gasket, you reduce quench... so you can actually end up with an engine being more detonation by reducing the compression ratio that way. Especially if you have an engine with a head design that is prone to detonation... like the N42 and N47 are.

Not saying that you can't make an N42/N47 combo work... but it will be less than optimal. And for crappy California 91 Octane fuel, I would definitely run H20/Meth injection as a fail safe with an N42 head. That's just my personal opinion mind you. 

Either way with a good intercooler and proper engine management you can run a higher compression ratio than what Nissan did back in the day. Programmable ignition timing and programmable fuel curves will go a long way on controlling detonation. 

BTW, I have a NA F54 Flat top with N47 heads and 10.3 to 1 CR. I have to be careful with ignition timing on that with 91 Octane.  Stock(ish ) distributor at this point. 

 

 

Hmm that definitely gives me a lot to think about, I've asked around on some different pages and was pretty surprised to see that more than a few people got some pretty high numbers out of the N42 combo.   350 whp out of a n42 head and block with dished pistons and all, with a blow through triple webber setup! Now that I know it can be done, I want to know what I need to do to make a SAFE 300whp if possible. P90 heads seem like they are getting increasingly more difficult to find (and more expensive). I could run a Water/Meth injection system on my MS2 setup and hopefully have some sort of fail safe for it. I will be running a good intercooler setup and do everything I can to keep the intake temps down. I'd like to install a sensor too just to see exactly whats going on in there. Lots of work to do and money to spend. And I need to find the right turbo still lol

CA gas is garbage. Very disappointing that I cant do better at the pump. 

Again I appreciate the feedback/help/advice! Its been a great help in leading me in the right direction. 

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91 isn't as bad as you think, at least not at sea level. Remember that elevation plays a roll in air density, higher elevations generally have higher octane gas available. I know that I can get higher octane gas on the east side of Washington than I can on the west side of the mountains, and it's pretty much the same performance because of different air density. 

Tony D showed you that crazy triple carb turbo engine, but remember these days you can get that much more easily and reliably. Old school guys run carbs, but even Tony will tell you that fuel injection is objectively better in every way to what a lot of those guys worked with, water/meth injection probably won't be necessary just at 300. Check out this Datsun Europe build, same block you're working with :) 

 

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