Twin Turbo 3 liter vs V8 Powerplants

[cyrus]

I have driven my car all weekend read hundreds of miles and have some thoughts:

 

I have had a:

 

2JZ-GTE (twin turbo 3 liter, 17PSI, I6 406 RWHP)

 

and have also built a

 

LS1 (5.6 Liter, 330 RWHP).

 

Both cars have 6 speeds.

Here is my inpression:

 

The V8 is smooth

The I6 rough

 

The I6 is more powerful

The V8 is weaker

 

The V8 sound cool

The I6 sounds lame

 

The I6 is very difficult to drive smoothly

The V8 power is seamless

 

In drag racing the I6 is easier to control due to it's slow building power

The V8 is difficult to control tire spin.

 

The instant power of the NA V8 is INSTANT

The lag of the I6 even with sequential turbos is about 1.3 seconds

 

The V8 has torque availble at all RPMS

The I6 has torque only when RPMS are high, the load is high, and the turbo is spooled

 

Even with the power difference going to the I6 people believe the V8 has more power (due to its punchy-ness)

 

The V8 runs on regular gas

The I6 runs on 100 octane

 

So to sum things up the I6 car is faster but their is a boat load o' difficulties that make it not as rewarding as it should be. My ideal engine would be big enough to make power on its own then have moderate boost to make it crazy. For instance the ultimate combo would be a LS7 with low compression and ~10 PSI for about 600 RWHP.

[Guest ON3GO]

The V8 runs on regular gas

The I6 runs on 100 octane

 

 

umm?

 

17psi on stock twins and you need to tun 100octane?

 

maybe you want to but thats very doable on pump gas.

i know plenty of supras and other high powered turbo cars that runs pump gas and makes more power then you and on either singles or upgraded twins.

heck ive done it too..

 

i agree with you on a few things but that gas comment just doesnt go for me.

 

mike

[J Taylor]

I wonder about the need for 100 octane myself. Lots and lots of guys running around in 400hp supras on pump gas.

 

Never heard anyone say a turbo supra sounds lame or is rough either. IMO, a turbo I6 is one of the best sounding and smoothest engines you could ask for.

 

BTW, my turbo L28 made peak torque (421 ft lb) at 3800 rpms and fell off as rpm's got higher. I would imagine a 2jz with the stock twins would make peak torque a bit earlier than that.

 

JT

[Guest ON3GO]

JT your right.. a stock twin 2JZ makes peak torque around 3500rpms, singles take abit longer if its very big.

i love the way a I6 sounds too.. and those 2JZ's just sound amazing when done correctly!

plus i wonder about the smoothness too.. those are some super smooth engines, way smoother then a L28ET and there pretty smooth for what they are!

 

mike

[Corzette]

Just my two cents worth. I have been around Zs for 20 plus years now and have drove L6s built and even a turbo. Your really comparing Apples to Oranges. Besides the sound differences, you cant compare Turboed engines to NAs, especially power differences. I guess it all depends what your looking for. If you like boost and the wow factor go ProCharged/Turboed LS1 etc, then theres no comparison with possibilities. In other words with all being equal.....theres no replacement for displacement and thats just the law of nature not my biases.....lol.

 

BTW, if you look at a typical turboed RB or 2JZ etc, you have some doing 11.00s at around 128 to 130 MPH. A mildly built V8 is doing it at only 120-122 or so. Torque is where its at and how fast you can get it and maintain it. 1.3 seconds lost on lag can mean 3 seconds down the quarter! Turboes make it up down the big end but sometimes its all over before it starts. Now just ask TurboMiester, he has the best of both worlds. Just some thought on my side. No bad on turboes just some food for thought.

 

Terry

[Mikelly]

The question you need to ask youself is what you want to do with the car... I say this a lot, I know, but it is especially true here. One reason I steered clear of the intoxication of boost is simple... complexity... Now Now, don't all jump up and throw a fit without hearing me out... If you take the "swap" portion out of doing the V8 or the Turbo, and once you've sorted and done the "Swap", then we're left with day in and day out driving, either on the street, at the track, or both... One simply can not argue the fact that a turbo'ed drivetrain is more complex, expensive and difficult to build and live with... it only takes a look into our turbo section to see the posts from members who are getting quite proficient at doing head gasket swaps.

 

Driveline upgrades are also a non-issue as the HP requirements climb, since 400HP is 400HP... Parts break because of the power, not because of the method chosen to make the power. Weight also will suffer, and maybe surpase the V8Z when doing a turbo application, as the unit, plumbing, intercooler, and electronics (if done properly) will add to the net gain in weight.

 

It is much easier to build a moderate compression V8, making 400-ish HP and living with it day in and day out, driving it in rush hour traffic, and being able to knock down low 11s... That is much more reliable, less expensive to maintain, and funner in the long run, because you are spending more time driving, and less time wrenching...

 

Just my $.02

 

Mike

[Scottie-GNZ]

Interesting post which I am sure will stir up a lot of debate and what it will really come down to is one's preference.

 

However, nothing irks me more than a general categorization of turbo cars. Cyrus should have said "My 2JZ setup" not I6 turbo, in general. I say this because of some of the statements he made about his setup such as "it's slow building power", "The lag of the I6 even with sequential turbos is about 1.3 seconds", "The I6 has torque only when RPMS are high", "The I6 runs on 100 octane". I was also a little surprised by the "The I6 rough" statement as my experience with that engine is that it is silky smooth.

 

This one could be debated until the cows come home and all most will be doing is expressing their preference. At least Cyrus has 1st-hand experience with both to express his results. Having buit 2 V8 Zs, I also have my preferences but boy, what I could do with an LS7 . Come to think of it, I would love to tweak a 2JZ myself.

[cyrus]

Mikelly hit the nail on the head. My car is crazy fast, it just that similar power made with a turbo is more complex, expensive, etc. I want people to have insight into this.

 

Scottie GNZ is right this only refers to my I6 meaning the supra. As far as smooth goes I think that once you remove XXX pounds of insulation from a supra you find that the engine actually makes some rattles. And the 1.3 (est)seconds refers to if I nail this car at 5000 RPM how long before this thing is in full spool, surprising slow, as the sequential system will not help this problem.

 

Additionally the octane requirements of my engine ARE high you can search this one out but it is generally agreed upon that all those BPU Supra ARE experience some detonation on 93 oct. And around here we only have 91 oct.

 

As far as the noise I am not sure but my lightened flywheel makes this thing rattle a lot. And the Getrag trans is known to be very loud to begin with.

 

Before too many people start working too FAST and FURIOUS on there cars these are some good point to consider if one like to street drive.

 

It seems I am alway trying to build the ULTIMA CAR but get disillusioned upon the way...

[mas28O]

Cyrus was the 17psi stock level? I cant wait to put my new ls1 back in my 240z, It should make 530rwhp on 91 pump gas NA. I love the LS1 in my RX7 448RWHP 10.9@128mph NA. I drove some fast turbo cars this weekend and I could not stand the lag, the only turbo car that made some good TQ was my friends 11 sec cyclone.

 

Cyrus we will be at Sears Point on Wednesday want to make it out? I want to see you run now that it is making some good power.

[johnc]

My preference, which really means nothing except to me, is for normally aspirated engines. Throttle response and a linear power curve are more important to me then just about anything else from an engine. I know its possible to tune a turbo engine to do both and the stock Audi 1.8T engine is a perfect example.

 

But, all the aftermarket and modified L6, 2JZ-GTE, and SR20DETs I've driver give up throttle response and a linear power curve for big horsepower numbers. It makes the cars difficult to drive fast at a road race track.

[Drax240z]

It is much easier to build a moderate compression V8, making 400-ish HP and living with it day in and day out, driving it in rush hour traffic, and being able to knock down low 11s... That is much more reliable, less expensive to maintain, and funner in the long run, because you are spending more time driving, and less time wrenching...

 

No way!!! A turbo gives you drivability gains big time. I can put my grandma in my car to drive and as long as she doesn't mat it, my car will behave as a 125hp fuel injected commuter. Hit the go pedal and all of a sudden there is twice as much power and torque on tap.

 

What's easier to moderate in traffic, a 300ft-lbs @2000rpm setup, or a 125ft-lbs@2000rpm setup?

 

And for boost response... 1.3 seconds at 5000rpm is NOT typical of most turbo engines, despite what some people experienced in the early days of turbochargers. (and consequently wrote them off as being laggy) A well designed turbo system has response almost no different than an NA engine.

 

V8's have lots of advantages, but the beauty of ANY turbo system is that you can have the best of both worlds, drivability AND power.

[Mikelly]

Richard, For everything you have stated, I can counter it... Especially with LS1s these days... Knocking down respectable fuel mileage and drivability is a non-issue... My Vette is 500-700# heavier than a Zcar and gets 26mpg with a modified setup. It also is extremely easy for anyone to drive, even your granny. My point is that, as Scottie stated, We can argue the pros and cons all day long, but you're gonna believe what you will, and so will I...

 

I remember getting into a discussion about this topic previously, right around the time I was building the stepson's turbo setup and how I weighed his honda turbo stuff and found that his intercooler, DT25 turbo, plumbing, and added support hardware about made me pass out when the box of stuff landed 63#s including the box... AND throwing in John C.'s comments about the drivability and tunability (Assuming a road race setup here, which is all I care about!), it is hard to argue the issues...

 

More weight than standard, and possibly more than a V8 if done correctly, and you simply won't be able to argue the complexity, and added possibility of failure of parts... more parts added into the equation simply mean more parts that can fail.

 

I'm not saying turbos are bad, and I've HAD and DRIVEN a turbo car and DONE a turbo swap (Not a Datsun or Honda, but still), but I stand by the comments above... And Nitros or superchargers fall into the same category as far as the failure/ complexity issue...

 

If I have a V8 (or L6) non turbo'ed car, will I have an issue with turbo oiling? NO. Will a piece of pipe coupling BLOW OFF under boost? NO. Will detonation become an issue? NOT under normal circumstances, and highly unlikely that is easily changed while driving! Will I have to worry about a BOV or Waste gate related issue? NO. Will EGTs be as much an issue to monitor? NO.

 

The list can go on and on... EVERYTHING that you would worry about a V8 or other powerplant suffering CAN be said about a Turbo powered vehicle... Unfortunately you can't make that arguement in the other direction...

 

Cheers!

Mike

[EvilRufusKay]

Cyrus' post is quite helpful for those like me that have little to no experience with turbo motors but are toying with the idea of installing one. In other words the general statements have merit especially when you know that he is not just whipping it out, but instead has built and driven both types of drivetrains. His post combined with Mr. Kelly's first responce make this thread useful. The debating is poinless as Cyrus (although he doesn't say it) is obviously speaking of his motor and not all Supra's, turbo's, octanes or whatever.....Rufus

[pparaska]

My first thought is that 1.3 sec of turbo lag is not common for a well setup turbo system...(that seems REALLY high)

 

Which gets to my next point - it takes a bunch more effort to do a DIY turbo setup, or even mod an OE turbo engine setup and get it to work like I'd want it to (no lag, reliable, drivable, no boost-induced oversteer in mid corner, etc.) than it is to buy or build and install a BIG ENOUGH normally aspirated engine.

 

Some people like the technical challenge of the turbo thing. Others just think that turbos are the only way to make the statement they want to make.

 

Me, I like my power start out high NEAR IDLE, have a linear delivery across the rpm, throttle position, etc ranges, and I like my setup to be SIMPLE and fool proof. It's very easy to do that with a bunch of displacement, no matter if the valvetrain includes pushrods, or not.

 

To each his own, but one things for sure - its just plain easier to bolt a large displacement engine in the bay than it is to engineer the killer 2.xL turbo setup to make the same peak power with the same drivability parameters.

 

Which gets me to the next point. If you're going to turbo, why stay below 3.x Liters? What's the point? Don't give me the gas mileage BS. I don't believe it. My leaky, super rich burning carbed 327 got 23 mpg to and from the first SEZ. With 6 cyilnder engines in the high 3 and low-mid 4 liter displacement range out there to turbo or super charge, why stick with a teeny little 2.x engine? I think the answer is that people like to show off and brag about how much power their teenie little engine makes on boost. Then they go home and work on changing that head gasket....

 

It's called the "I like to be the underdog" mentality.

 

Turbo a V6 or V8 - use low pressure boost, and high compression. You'll like it better than tweaking the tune on that grenade and fixing it all the time.

 

High boost, small displacement is for race track and the PROFESSIONAL driver in a purpose built race car. A street based car (what the Z is) weighs too much for this to work well, on the street or road course. The one place I can see it working well is at the drag strip. But how many of us have a drag-only Z? On the street, turbo lag SUCKS. (ask me how I know - I drive a laggy turbo car every day). On the road course, the last thing you want is the lag to cause the boost to come on in mid corner and upset the car. Sure, you can tune your driving style around this, but being smooth with such an engine is a handicap, if your doing HPDE's. Any engine is legal for such uses of the car, so why shackle yourself with a puny engine with a ton of touchy technology heaped on it to make power?

 

Answer: "Turbos are so cool and pushrods are for tractors"

[Phantom]

Since this is really a straight line performance discussion - Go to the local GM dealer and buy the 3yr/36,000 mile warranteed supercharger option they offer for the LS1 that bumps it another 100-140 HP, throw a built 4L60E or 4L80E in behind it and watch the I6 get left in the dust - with all factory parts that are factory warranteed.

If it's about what you can get out of a motor I am absolutely amazed at the guys that get these unreal HP & torque numbers out of 6's. Major Kudo's. But, if it's day-to-day driveability with a lot of punch and "reasonable" fuel economy then I'll opt for the V8 - which is exacly what I did after agaonizing over the decision for 5 years.

[mobythevan]

If you're going to turbo, why stay below 3.x Liters? What's the point?

 

Less money, time, fabrication for me. I think the z cars are a special case for turbos because you can easily swap the 81-83 engine in. Now aside from that, if I am going turbo and not swapping the 280zxt engine, then I agree, why stay at a small displacement if you are going to have all the fabrication and costs anyway. As long as I have worked on turbos I have still believed the no replacement for displacement line. Start with the biggest cubes you can fit and then add boost if you want too much power. (which is what I want, but not for the z car)

[cyrus]

Total power is all that matters. Start with a big engine then turbo it! I agree!, but since I live in the socialist republic of california. I wanted the most powerful OBD 1 motor I could get incase I ever am required to smog this car. Technically I could do smog this thing under the 1994 standards.

[Drax240z]

Well obviously some of the older guys here are pretty set in their ways... :D j/k

 

For reference, my car weighs 2440lbs with turbo swap, big intercooler, recaro seats, full interior, roll cage, R200 swap, 10" sub, big amp, other speakers, and sound deadening. I don't know exactly what the turbo swap added, but I would hazard a guess that it was less than 40lbs, which except for an all out, balls to the walls race car I think we can consider negligable.

 

I think for the Z to be a good all around sports car, it needs a minimum of 2.8L displacement as well. I would certainly jump on the chance to have more displacement, but I'd have a turbo as well. (I like the power delivery, I like the advantages, even if no one else believes there are any) For a given power level a turbo equipped car is more efficient than a non-turbo equipped car... hence the reasons so many OEM's are going that route these days.

 

As for drivability, power coming on in corners, etc. I find with a bump in compression from stock, and the stock T3, as well as a lightened flywheel, free flowing exhaust, and agressive timing, that there is no issue with boost hitting in corners and upsetting the car. The power delivery is quite linear compared to many other turbo cars I've driven. (DSM's, SR20DET equipped cars, etc) My car may not have tripple weber throttle response, but honestly I think with a GT series turbo that is sized for mid range, I'm going to be damn close.

 

I think over-turbo'ing an engine these days is a bit like the overcamming of engines that was happening for so long in the good old days. Too much cam isn't a good thing. You might make nice dyno numbers but beyond that you are suffering...

[pparaska]

I think for the Z to be a good all around sports car' date=' it needs a minimum of 2.8L displacement as well. I would certainly jump on the chance to have more displacement, but I'd have a turbo as well. (I like the power delivery, I like the advantages, even if no one else believes there are any) For a given power level a turbo equipped car is more efficient than a non-turbo equipped car... hence the reasons so many OEM's are going that route these days.[/quote']

 

No doubt there's an advantage to a mildly cammed turbo motor in efficiency during cruise, over a lumpy cammed V8. But the differences are minimal. Sorry, I just don't go along with $2.50/gallon being expensive for gas like some people complain about, so 20-ish mpg doesn't bother me. I live close to work though.

 

As for drivability, power coming on in corners, etc. I find with a bump in compression from stock, and the stock T3, as well as a lightened flywheel, free flowing exhaust, and agressive timing, that there is no issue with boost hitting in corners and upsetting the car. The power delivery is quite linear compared to many other turbo cars I've driven. (DSM's, SR20DET equipped cars, etc) My car may not have tripple weber throttle response, but honestly I think with a GT series turbo that is sized for mid range, I'm going to be damn close.

 

You're describing a very well designed system with a 2.8L engine, and probably not a huge amount of boost. You also mentioned more compression than stock. These are along the lines of what I was mentioning. The smaller engines in heavier cars (DSM - I drive one daily) depend on boost for their power, so off turbo they are very lazy.

 

Turn up the wick and the difference between on and off the pipe is large and when it hits, it unsettles the car if it's in a corner, or makes a ruckus on the street and draws attention. Sorry, that's only good on the drag strip IMO. Or for chassis dyno bragging rights. (Mine's bigger than yours! )

 

[i think over-turbo'ing an engine these days is a bit like the overcamming of engines that was happening for so long in the good old days. Too much cam isn't a good thing. You might make nice dyno numbers but beyond that you are suffering...

 

AGREED! Yeah, take a 1.6L engine, throw 30 psi at it and it'll make lots of power. Try living with it on the street though - you'll end up hating it like the guy with the 300 degree duration cam in is V8 - except when it's at the drag strip.

[Owen]

I couldn't live with 1.3 sec of turbo lag...I drive a Z32TT every day to work and there's nowhere near that much lag. You didn't specify what turbos, or I missed it, but you CAN go smaller for drivability or even use hybrids that spool up fast and make high boost. Or how about a mis-firing system to keep the turbo spooling?

 

A couple of VATN (variable area turbine nozzle) units would probably be pretty fun on a 3 liter.

 

I can agree and disagree to many posts in this thread at the same time. Sure instant power off the line is cool, but I don't want it all the time. I like that, "ohhh, sh!t....here comes the boost" feeling. But yeah, turbos are heavy and expensive and complex. It all depends on where and how you intend to drive it.

 

PS, there's instant power for sale in my signature.

 

Owen