The following is the a distilled version of the Frequently Asked Questions and discussions (FAQ) about

Turbocharging the Z car

as discussed on the Internet Z car club.

[The Internet Z car club is an international mailing list with over 125 members and transmitted to a member's computer account over the internet.]

All information published here is the property of the original authors who are members of The IZCC and may not be reproduced for commercial purposes

Everything stated here is based on the experineces and opinions of the original authors. The authors and editor accept no responibility for any damages arising from use of this information.

Questions and Answers:

Q: What is the best engine-head combination for turbocharging?

A: The hot setup for turbo z heads are the later model turbo ZX heads.

Nissan has done some good work with combustion chamber design directed toward detonation control. Detonation control is all you need to worry about in a turbo motor as far as heads go. Don't mess with the valves or othersuch stuff. The huffer will get more air in the cylinders than you can use anyway. I concentrate my efforts on detonation control and then tractability and smooth running off-boost.

Q: Whats a good place to start doing research ?

A: Pick up the HP book "Turbochargers" by Ray McInnis.This is the bible for home constructors. Ray has a chapter on engines such as the Z. Next, as Jerry Pournelli writes in Byte Magazine, "If you don't know, find someone who does."That means working with Turbo Tom or TurboTech or other companies that specialize on your engine of interest. I generally stay away from companies that try to be horizontal and build kits for all different types of cars. The Z engine is just plain difficult to get serious horsepower out of and remain reliable.It can be done but it's a speciality.

Q: What have other people done? ?

A: I've built several turbo motors for myself and my customers. I used to build from scratch but I've found Turbo Tom's kit to be better than anything I'd be willing to do. His big win is his custom cast manifolds. The turbo bolts directly to the exhaust manifold flange. No connector pipe to corrode, sag, or leak. Tom and I disagree on fine details but then that's what makes things fun. My major complaint is that Tom has had an aversion to electronics and instead uses Holly carburators which I consider to be nothing better than a metered gas leak!In my last conversation, he did state that he's now looking at packaging an aftermarket fuel injection package with his kit. That will be a super win.

Q: How do I keep myself from blowing the engine?? ?

A: There are 3 big ingredients to building a reliable high horsepower turbo Z motor. First and formost NO detonation is to be allowed EVER. Stock pistons break like glass and forged pistons use oil like mad.Second, do exactly what those of us who have gone to the School of Hard Knocks tell you to do. My tuition to this school ranges into the many thousands of dollars. Third, keep the RPM below 8000. The engine has a terrible crankshaft resonance in this region that will break cranks in two. A properly tuned Z-motor will give you all the power the chassis can control well below this limit. Here are some specifics:

  1. You MUST O-ring either the head or block.I perfer the block because you don't have to redo it every time you clean up the head.

  2. You MUST use water injection if you want to use more than about 5 psi of boost, especially if you don't have a set of turbo-zx heads.I'm kinda fond of 20 psi boost myself. Turbo Tom sells a very nice, proven kit. Whatever you use must be able to deliver serious volume. You'll typically use a gallon of water per minute of full boost operation. The little windshield washer-based systems just ain't got it for this application.

  3. You MUST use the MSD ignition system with the optional pressure retard module. Don't bother building a motor if you don't spend this extra $300. Just burn the money.The pressure retard unit has a pressure input from the manifold and retards the spark at an adjustable rate per psi of boost.

  4. You MUST learn to avoid detonation at all costs.I've taken a Carter Detonation feedback module and modified it to simply dump spark whenever it detects any detonation.Since pistons are about $400 per set, this is cheap insurance.

Q: How much is this going to cost ?

A: I've got over US$10,000 in my current engine.You could probably do it for half that if you are really careful about costs. I repeat again. If you're not willing to go all the way down the path to make a detonation-proof motor, just build a fire with your money.You'll at least get to see the flame that way.

Q: I have heard that a blown, hgh compression L24 could do better than 300hp?

A: A blown high compression Z engine does not exist - at least for more than one run.Blown LOW compression L28 engines will easily produce over 400 hp on premium pump gas and water injection.My engine is not yet optimized and yet my coastdown calculations indicate in excess of 400 hp.

Q: Does a 240Z body need strengthening?

A: Yes.There is significant nose twist when the boost hits on a 400 hp motor.Unfortunately there is little room for additions under the hood. A roll cage will help immensely for the main body.I have not yet addressed frontal chassis flex but I probably will after I finish with the motor.

Q: How about the drivetrain ?I have a 280 diff + 5 spd already.

A: It should be fine.I add an additional nose anchor to the third member to stop bushing windup and the attendant vibration and I add a vertical transmission support on the rear for the same reason but neither are eally necessary.I'll qualify my statement by stating that I never engage in drag racing-type starts.I don't think the drivetrain would stand up to this very well.

Q: Many new cars are turning to computer controlled blowers.Is this a simpler alternative to turbo?

A: 'm interested in blowers, too, to get rid of turbo lag. The problem is you will be on your own and the lessons are likely to be expensive.

Q: How long do turbos last ?

A: Turbos in general last as long as their care.I got a hint early on about my 79 Mustang with a Turbo.Changed the oil every 2500/3000 miles.And equally important, never run he turbo without oil pressure, with includes on start up after changing oil.The turbo runs at high speeds, even at idle, and running it dry is what wears them out. Filling the oil filter with oil before installation is always a good idea, even on non-turbo engines. Also, let the car idle for a minute or so after driving before you shut it off. This prevents oil in the turbo from "cooking" because of the high turbine housing and bering temperatures after hard driving.

Q: Can anyone give me the approximate cost for a replacement turbo core?

A: Turbo City in California has either full replacements for around $450 or cartrige replacements, where you only replace the guts, for a lower price. They also have different size comp/turbine cores which may be useful if your considering turning up the bost (13 psi= approx 250 HP on stock turbo motor w/ 7.4 comp. ratio).

Q: Given enough money, could I boost my HP from the "normal" 180 to approximately 250 ?

A: Using the acceleration/coast down method of measuring road horsepower outlined in "Turbochargers", my 30 psi boost L28 Z engine makes right at 400 hp.Around 300 at a more sedate 20 psi. Strange things happen at these boost levels.Ya dump gobs of gas in to start a fire and then pour in the water to try and put it out!


TurboCharging early Z cars:

I talked to Tom at Turbo Tom's this week.In addition to very excellent turbocharger kits for Z cars which include custom cast manifolds, ...

Out of curiosity; how much does such a beast cost?Can you safely put

them on a non-zx motor?I know the official turbo version of the block has some additional `web' in the water jacket between cylinders, presumably to strengthen the block against the extra strain.


I bought one of his kits in 1984 and it cost about $4000.This included having head work done, O-ringing the head and a Racer Brown Cam and valvetrain.(O-ringing is absolutely, positively mandatory even for a 5 psi system.)This also includes the MSD pressure-retard ignition system (mandatory).

This system is capable of boost in excess of 30 psi.Needless to say the performance is awsome.At 18 PSI of boost, about the limit for cast pistons, the body is twisted visibly whenever the boost kicks in.Tire spin a will in 1st and 2nd with 205/HR14Michelins.At 10 psi boost, I clocked 155mph on my radar gun.This is on a 75 model 2+2 with no improvements other than a small air dam in front.

This car has been in storage since about 86.I've just resurrected it and am redoing the engine with forged pistons so that higher boost can be experimented with.And if that's not enough, Tom also sells a nitrous oxide kit custom designed for the turbo installation.

Problems -

The biggest problem is with fuel.At 15 psi boost, high volume water injection is mandatory.This means that the interval between garden hose stops is short.And if this system fouls up (clogged jet, for instance), you loose a piston or 2 before you can react. I know !

The second problem centers around the carburator.OR more accurately, the fact that he uses a carburator at all - a Holly 490 cfm 4-bbl. I hate carburators.Especially when they are located in a hostile environment like right above an red hot exhaust manifold.Tom did tell me in my recent phone conversation that he is now supplying kits with the Austrailian (sp) electronic fuel injection system.This should completely address the fuel problems.

My next complaint is that the system really needs an intercooler.Tom is of the KISS school of thought but with today's near-kerosene for fuel, some sophistication is necessary.I'm currently working on an air-to-water intercooler for the package.This should solve this problem.

Finally, the exhaust.This system needs a lot!Tom supplies a 3.5" diameter outlet pipe for the turbine.A 3" exhaust out the back is essential.Tom Supplies a 3" SuperTrapp muffler.This muffler works but is ugly as a dog and tends to drag because it cannot be mounted high enough on a stock-bodied Z.My interim solution is a large diesel truck muffler that fills the length of the drive tunnel. I still get several PSI backpressure.My next step is going to be to fabricate a custom muffler to fit in all available space in the drive tunnel and to have adequate flow.

So, do I recommend the kit?Hell Yes!!!!There is really nothing on the road that I have to fear as far as speed goes.The 928 and late model Corvette owners are the most fun.I've kept my Z looking almost totally stock.The only give-away is the 3" exhaust stinger and the LARGE cloud of grayish smoke under WOT compliments of the fine water injection. Oh, and the turbine whine :-)

This is not a kit for the guy who has to work on his car on the curbside. Even though the kit is as complete as practical, one still needs the ability to fabricate small parts and to do light machining (easilyhandled with a drill press and a traverse table.)You should also know a lot about tuning and know intimately what the term "hand grenade engine" means.That little boost control knob could as be named "dial a hole", piston-wiseYou must have a conservative slant and recognize the limitations of today's fuels.Properly intalled and conservatively operated (no pinging allowed), an engine should easily go 60-100,000 miles.I've personally put over 100,000 on another turbo motor.

Modifying Turbo ZXs:

I've been investigating some options for increasing the power of my 82 stock turbo.It seems to me that you should be able to run thestock engine to the 250-300 HP range without worrying about internalmodifications (like upgrading the connecting rod bolts, ect.).Whileit is certainly possible to go past 300 HP, not only do you have toconsider internal matters, but things start getting very expensive.

I'll layout some of the 250 HP range modificaton issues and wouldwelcome any comment on the wisdom of this possible approach.

The first order of business is intercooling.I've been looking at an air/water unit from Car Tech in TX. The kit includes in car boost level adjustments and a recalibration procedure for the intake manifold popoff valve.This kit is $750.

The stock EFI setup will work fine up to 9 psi (stock runs 6-7 psi).This alone gains approx. 45 HP.Corky at Car Tech also has an EFI enhancement kit for $250 which increases the fuel pressure to the injectors while under boost levels above 6 psi.The unit is adjustable and uses both the absolute and rate of pressure change to control the fuel pressure.It would be nice to use an aftermarket EFI system here, but these units start at $1000. This would allow for the 13-14 psi range I mentioned.I feelthat 15 psi is a good practical limit which avoids the needfor water injection systems.

Ok, lets get back to the turbo unit.From what I've been ableto find out, the stock garret T3 unit should be able to handle12-13 psi without over spinning.I think this is not an importantworry however since the stock turbine was selected to run around6 psi.This means that while it may be able to make 15 psi allday, it won't do it efficiently.This is where an upgraded turbinecore from Turbo City (or elsewhere) would be a plus.

The bottom line: $1000 for the intercooler and EFI kit gets youapprox. 250 HP.If you need a new turbo anyway, a larger capacityunit and larger exhaust system combined with the above gets youcloser to 300 HP.

Turbo 300ZX Disscusions:

I've got a 84 Turbo 300ZX, and I've got similar problems with the V6 turboconfiguration.. Ever since I've owned the car (I bought it in 1990), I've had a fair amount of electrical system problems in relation to the EECU.I finally decided that the Turbo configuration with the V6 (for 84 models anyway) literally cooks the wiring harness, due to insufficient shielding.Anyway, back to the original post, my 300ZX also exibits this "lag" tendencybut without any "noise"..If I have the hood open, and I hit the throttle a bit hard with my hand and let go real quick, the engine actually slowsdown before it picks up to the "requested" RPM... I've never been able todetermine what that problem was!This could be "correct" behavior.I noticed this when I had injection on my 260 (transplanted from a 280).After reading about L-jetronic, I understandthat low speed throttle response is a weak point in these systems. Partof the problem is the inertia of the flap in the air flow meter, but also this type system doesn't really know you are trying to accelerate until you hitthe "full throttle" switch.There is also an "after idle" enrichment but itis a short timed pulse triggered by opening the throttle from idle.Of course the system on the turbo may be different.

Turbo Oilers and Cool Down:

My "opinion" about the oil pressurization system is that it "could"be usefull on a turbo car - I doubt it is worth the money or trouble ona non-turbo. JGDmentioned letting the engine idle a bit before shuttingdown after hard running. Well, some of the numbers I have seen mentionedby manufacturers is on the order of 1 minute. That is an annoying amountof time to sit around each time you park your car. The questions thatI would look into when considering such a purchase would be

  1. How longwill I keep this car

  2. Does the car have a known problem with cookingturbo bearings

  3. Will this device cause warranty aggravation.

The device sounds plausible.You have nice amount of oil flowing on that rapidly spinning hot turbo bearing - its got to do some good. Worth the trouble ? It all depends. How about designing a simple circuit that when you turn off the engine, it maintains the connection to keep the engine running for 60 seconds while you jump out of the car and lock it. (You would probably get lots of funny looks like the old Cadillac owners that left their lightson!) Optional circuit sensing the engine temp off the internal sensor would only allow the extended time for high engine temperatures. An op-amp and possibly a 555, transistor and a relay wired to the ignition should about do it.

moderator: That would work, as would an industrial time delay relay. I would like to point out, however, that the cooling starts at the moment the engine last comes out of boost. So if you idle to your parking place or down your driveway or whatever, you've already put in a significant part of any cooling.As a practical matter, I've never had any problems allowing enough time between my last boost and shutdown.

Yes, a minute is a drag...BUT...if you start the cool down processby coasting a bit prior to being parked, you'll save yourself a bitof time. (But jeez folks, it's not like one minute out of your drive time is going to kill you when weighing the possibility of slaving overyour engine for several hours replacing the spent snail...not to mentionthe cost.)I have the original turbo in my Volvo (sorry it's not a ZX...) with abit over 110k miles on it. Nary a problem on the positive pressure side of the intake manifold...Since new, I've adhered to the 1 min. cool down period. (I guess the aux. oil and water coolers help too...but really wouldn't do a thing once the engine is I coast and cool).

final editing by Salman SHAMI.