Turbocharge or stroker: which to build

[Tbob]

MY 73 240Z, very clean and runs fine with dual Hitachis and a header, no smog stuff.

 

I have a 79 L28 NA motor complete, which I was in the planning stages of turbocharging, adding Megasquirt EMS and coil on plug. Goal was 300 whp. I contacted a motor builder to get the block prepped (cleaned, honed, new bearings, etc.) he came back to me with a proposal to build a stroker L28 instead. He is confident of 300-350 whp with no turbo.

 

He proposes diesel crank, K20 or L24 rods, custom pistons, ported and polished head, some cam work, larger injectors and newer intake. He feels there is better durability and reliability with less stuff under the hood (Intercooler, turbo, piping, etc.) He makes some good points, but I’m torn between the two builds. 
 

what sez the turbo gurus here?

 

 

Edited October 25, 2021 by Tbob
Typo

[rturbo 930]

Who is the builder? Datsun Spirit? 300whp is a ton of power for an L stroker, and 350whp is all out race build territory, unless you get one of the DOHC heads that member Derek has been working on. 

 

What is the intended use for the car? If you want a street car to cruise around in, I'd go with the turbo option, since you can have a pretty tame and streetable 300whp turbo engine. Probably a lot cheaper too compared to getting that kind of power out of an NA stroker. 

[AydinZ71]

Agree with @rturbo 930. The L series head is not designed in a way to meet simultaneous goals of high output and street ability. I mean, for the time it was designed it’s a fantastic engine. 

even when you put in a race cam with high lift and long duration, the 2-valve setup and modestly sized runners are going to limit you (even on a P90). There are some bench test results out there that shows the L series head flows only a fraction of what a modern DOHC I4 can handle, like a k24 or even an SR20. 
 

All this to say, getting above 220hp on a 3.0L stroker will start to exhibit loss in daily driving ability, considerable loss of gas mileage, and some big expenses on head work. Upping the RPM band on a stroker also means big expenses on lightweight rods and pistons.
 

I definitely suggest an L28et setup. I have one in my street Z pulling 300hp with no issues, 15 years of reliability, and modest turbo lag. Very streetable 
 

 

Edited October 25, 2021 by AydinZ71

[madkaw]

Has the OP ever driven any modified Z? 

It's a hoot with 230 NA  rwhp.  I would say it's pretty reliable since that's not crazy numbers.

You are almost close enough to come up and take a spin in a stroker. 

Anything over 200 would be fun. Can't compete with todays fast cars , but it will be a fast sports car. 

I think I sold my L24 for a dude in your area that had a 73  

And I think the NA numbers you were quoted are unrealistic 

Edited October 26, 2021 by madkaw

[Tbob]

OP here. Thanks for the insightful replies - just what I was looking for. I have not driven a Z with higher HP, so 300hp could very well be more than I need.

 

I plan to take your points to the engine builder and see what he thinks. He’s a reputable shop that specializes in Z cars, so I think our conversation will be positive. I may not have made my goals clear, so naturally he came to me with HIS vision.

 

Aydin, I would really like to know your turbo build specs. Reliability and streetability are important to me, sounds like you may have the right formula. You can PM or post here, I’ll be sure to reply.

 

bob t

Edited October 26, 2021 by Tbob

[madkaw]

I would question that builder if he is confident he can get 300 -350 NA rwhp and still be streetable . MAYBE crank hp .

One would have to run 13:1 and a huge cam.

I have 226 rwhp and can do a 1/4 in 13.1 and 0-60 4.5 approx . My point is that bigger hp numbers sound good but it doesn’t take much with a 2500lb car. 
Good luck 

 

[rturbo 930]

54 minutes ago, Tbob said:

I plan to take your points to the engine builder and see what he thinks. He’s a reputable shop that specializes in Z cars, so I think our conversation will be positive. I may not have made my goals clear, so naturally he came to me with HIS vision.

Is the engine builder Datsun Spirit? He's a capable engine builder by all appearances, but some time ago I noticed that the estimated power figures that he lists on his site with his different engine builds went from being crank HP to wheel HP. As crank HP figures, they were impressive, but feasible, but as WHP numbers, I think they're outlandish, and I question his ability to follow through. 350whp would be about 400hp+ at the crank which is what the all out drag race motors they build in Japan make. 

[Tbob]

Builder is Z car guy in Cincinnati . Figures may well be crank hp, since he's not doing the car, only the motor. 

 

https://www.facebook.com/zcarguy/

 

I don't want to be in a position where I feel I have to defend the builder. My information is only from mail exchanges, and his reputation in town. I'll be sure to let you all know how it progresses.

Edited October 26, 2021 by Tbob

[JMortensen]

Turbo. An L at that power level will have a lifespan measured in hours. I've driven zredbaron's stroker with 300 bhp. It's a lot of fun. Also requires race gas and is fragile.

By comparison, I have a 2L 4 cyl GTI with somewhere in the 280ish bhp range (based on the tune and mods) and I can drive it on pump gas, and I don't feel like it's in imminent danger of catastrophic failure.

I would suggest if you turbo it that you ditch the entirety of the intake/exhaust systems and start over, new manifolds, bigger turbo, intercooler, tunable FI, get rid of flap door AFM, etc. 

If you were going to put $10K into a stroker, I'd look at spending that money on swapping in a better engine that is already turbo'd and doing it that way. L series just has too many limitations, IMO.

Edited October 26, 2021 by JMortensen

[Tbob]

My motor is a NA, so there’s no legacy turbo equipment to deal with. JM, can you suggest manifolds, turbo, TB and other parts I should look at for a reliable build? I plan to go with a Megasquirt ECM.

[JMortensen]

No, sorry. Just convinced that the stock intake is restrictive and the stock turbo exhaust manifold has a T3 flange and is a crappy log manifold design. 

[AydinZ71]

@Tbob Here is my street car (turbo) setup:

 

- Complete L28et motor from late model 280zx. That is to say it has an F54 block and a P90a (meh...hydraulic lifters) head. 

- I tapped the OEM gas tank drain plug to create a new 3/8" hard line from the bottom of the tank through to the engine bay. I did this literally when I was 16-17. In hindsight I was being cheap and this is not a recommended solution. 

- low pressure pump to the engine bay, filling a fuel surge tank. bottom nozzle feeding a walbro 255 high pressure fuel pump. From there it is regulated by an aeromotive "return" style regulator that drains into the surge tank. Finally, the tank has a nozzle at the very tippy top which overflows back into the OEM fuel line, back into the fuel tank. I was OBSESSED with building a reliable fuel system to avoid lean/knock. 

- OEM intake and turbo manifolds. There were not affordable options at the time. 

- T3 "Super 60" compressor wheel trim. I think these are rated to about 325hp.

- OEM MKIV supra Intercooler with 2.5" steel tube plumbing and an HKS racing (large diameter) BOV

- Bosch (76'?) Mercedes diesel high impedance 420cc injectors

-OEM downpipe and 3" exhaust terminating in a magnaflow straight-through muffler 

- Simple Digital Systems (SDS) EFI system. Uses crank angle sensor with little magnets I drilled into the pulley. 

- 280zx turbo distributor used only to distribute the "spark" to the right plug. Ignition timing managed by SDS\

- OEM clutch disk, with dual pressure plates. Holds the torque

 

At 16psi, she was making a hair under 300hp, and about 310ft-lbs of torque if I remember correctly. Overall a modest tune.

This was all assembled nearly 20 years ago. I daily-drove for about seven years, then on-off for the last twelve. I mentioned she ran reliably for about 15 years because I sold her 6 years and bought her back last year. New owner did not have any complaints, and did not touch the engine. Engine has had absolutely no mechanical problems. Wore out a Walbro pump, and the turbo is nearly dead. Shaft play, and burns oil at spool-up. 

 

I have been assembling parts for the next iteration. Here is what I have, just waiting for the race car to be done:

 

- Protuners intake, exhaust manifolds, and downpipe. Exhaust and manifold have shipped, and already got the intake. 

- CD00A L-series trans adapter designed by Derek (a member here). Nissan 5-speed is borderline over 350 ft-lbs. They are going for nearly $1k here in LA, so id rather just sell it or keep it for the race car. 

- Wlad's Ford super 8.8 diff cradle, CV's, and hub uprights. all aluminim case "Torsen" (Helical) LSD diff a 17' mustang GT automatic

 

Still to be purchased

- eyeing a G30-550 turbo from Garrett. They are nearly $2k though, but have enormous potential 

- larger injectors

- larger fuel pump

- air-to-water intercooler, and plumbing

 

These next upgrades will not be done until I get the car on jack-stands and stiffen the chassis. getting too far over 300 ft-lbs of torque without stiffening the thin sheet metal unibody on a 240z is not advisable. I am sure I am forgetting something. Feel free to ask.

 

-Aydin 

Edited October 27, 2021 by AydinZ71

[AydinZ71]

I would just like to point out how multiple people on this thread are more or less saying the same thing, and have a pragmatic sense for these things based on direct experience. This didn't happen when I was younger. There would be disagreements on figures, and those promoting outlandish numbers would often win the ego wars. This explains why I enjoy this forum over facebook. Gathering very experienced people into one part of the internet for free without all the trolls is an accomplishment of note. Now lets just manage to not get "canceled" LOL. 

[Tbob]

9 hours ago, AydinZ71 said:

Here is my street car (turbo) setup:

Aydin, thanks for the great write-up! I can see what you’ve done (and learned) as well as where you’re headed. Lots of good info for me. That Protunerz intake is sick. I want one.
 

I second your sentiment on the quality and thoughtfulness of the responses here. That’s why I’m posting here rather than one of the “social” sites. Thanks to all who contributed. I’m back on the turbo bus. 

Edited October 27, 2021 by Tbob

[Dat73z]

You already have a lot of great responses here. Not sure if there is a local Z community in KY but if you have the opportunity see if you can drive a stroker L and a turbo L to see what makes the most sense. IMO even a mild stroker or mild l28ET is a lot of fun in the light s30 chassis. The L28ET is likely going to be the best bang for your buck. My friend just got their 3.1 Rebello stroker race car with triple Mikuni 44's back on the road and if you're going to build it all of those parts and work are not cheap. If you really want to light money on fire you could do both a turbo and stroker but you could also move off the L series and get a lot more unless there is a nostalgic reason to stay L. 

[AydinZ71]

10 hours ago, Dat73z said:

You already have a lot of great responses here. Not sure if there is a local Z community in KY but if you have the opportunity see if you can drive a stroker L and a turbo L to see what makes the most sense. IMO even a mild stroker or mild l28ET is a lot of fun in the light s30 chassis. The L28ET is likely going to be the best bang for your buck. My friend just got their 3.1 Rebello stroker race car with triple Mikuni 44's back on the road and if you're going to build it all of those parts and work are not cheap. If you really want to light money on fire you could do both a turbo and stroker but you could also move off the L series and get a lot more unless there is a nostalgic reason to stay L. 

yep, I have a V07 crank and N42 core at the machine shop now. Sonic testing wall thickness, and deciding where to go from there. 

[Dat73z]

@AydinZ71 yep I had a similar dilemma...was moving and contemplated selling all of these random stroker parts I had laying around. Ended up dropping them off at Rebello since he was local to me and getting a 3.2 turbo stroker built. A monster NA would've cost about the same since labor is pretty constant

[madkaw]

Fun driver is subjective for sure . I also say that the OP might be happy with a well build 2.8 . We know it’s all about the head . Spend 3000$ on a good head, accessories  and get 200hp + which will make a fast z and also be user friendly around town . One could make the head the building block . These bottom ends are pretty bullet proof stock . 

[AydinZ71]

@madkaw agreed! 

 

Only distinction I’d like to make on the bottom end is that you are getting close to square bore/stroke with a stroker setup (86/83). I couldn’t say how much your short-block redline is de-rated from a standard L28, but the extra stroke will put higher acceleration forces on your rods. Since F=MA, you get the picture. For an NA engine, your most likely bottom-end failure point is blowing a rod at high rpm due to excessive rod acceleration forces. Therefore, if you are running a mild cam and using it for street applications I 100% agree you should put all your money into the head and just use OEM piston/rod

combos (Z22piston/l28 rod for example). 
 

However, if you are going wild with the head: race cam, beehive springs, upgraded retainers. At some point, your heads RPM potential will exceed the bottom end of the stroker engine. 
 

If I choose to use the my V07 crank for an NA application, I intend on going with lightweight AM rods and pistons to alleviate the momentum forces from a near-square bore/stroke (again, F=massXaccel)
 

In contrast, my L24 race engine is ALL head, with an OEM block. She should be able to run through 7500 reliably. Greg Ira runs his out to 8200, but has swapped in the right rods to make it happen reliably, and our shitty 4-spd class rules means we need to go well beyond peak HP before shifting. 

Racing application: 
This might be a controversial opinion, but running an L-series past 8500 is kind of silly to me. The head just won’t flow what you need to maintain torque this high. Your torque is going to start nose-diving after 6k rpm even with 320+deg valve opening durations. Therefore, the gain on you HP influenced by more RPM is not enough to counter the nose-diving torque. Especially if you have good gearing, why run the engine out so far, if your peak HP is somewhere between 6-7k?  
 

Anyhow, I’m sure some folks will disagree with me and I am comfortable with that. To save us time, I concede and you are right 😂😂

[madkaw]

7 minutes ago, AydinZ71 said:

@madkaw agreed! 

 

Only distinction I’d like to make on the bottom end is that you are getting close to square bore/stroke with a stroker setup (86/83). I couldn’t say how much your short-block redline is de-rated from a standard L28, but the extra stroke will put higher acceleration forces on your rods. Since F=MA, you get the picture. For an NA engine, your most likely bottom-end failure point is blowing a rod at high rpm due to excessive rod acceleration forces. Therefore, if you are running a mild cam and using it for street applications I 100% agree you should put all your money into the head and just use OEM piston/rod

combos (Z22piston/l28 rod for example). 
 

However, if you are going wild with the head: race cam, beehive springs, upgraded retainers. At some point, your heads RPM potential will exceed the bottom end of the stroker engine. 
 

If I choose to use the my V07 crank for an NA application, I intend on going with lightweight AM rods and pistons to alleviate the momentum forces from a near-square bore/stroke (again, F=massXaccel)
 

In contrast, my L24 race engine is ALL head, with an OEM block. She should be able to run through 7500 reliably. Greg Ira runs his out to 8200, but has swapped in the right rods to make it happen reliably, and our shitty 4-spd class rules means we need to go well beyond peak HP before shifting. 

Racing application: 
This might be a controversial opinion, but running an L-series past 8500 is kind of silly to me. The head just won’t flow what you need to maintain torque this high. Your torque is going to start nose-diving after 6k rpm even with 320+deg valve opening durations. Therefore, the gain on you HP influenced by more RPM is not enough to counter the nose-diving torque. Especially if you have good gearing, why run the engine out so far, if your peak HP is somewhere between 6-7k?  
 

Anyhow, I’m sure some folks will disagree with me and I am comfortable with that. To save us time, I concede and you are right 😂😂

You are so wrong - lol

Like you say - most power is made below 7 and the stock block is just fine with that . My cam has hp peak at 6k and peak torque at 4300 . Throw a MN head on there and be able to run 11:1 on pump gas and bingo - a fun fast car . 
I do want to cam mine for 8k though . It’s built to take that and after driving a M3 I want that rpm - if I don’t loose the bottom end . 
Options are plenty !!!