destroked or regular vq35 engine build

[TheHat]

A couple friends and I were talking about what we are looking to do with our z cars and my friend had mentioned how he wanted to take his vq35 and build the block and then turbo it. Now I recently had done some research on destroking and stroking (since I am up in the air as to what the future of my car will be N/A or FI anymore) so I suggested destroking it and then turboing. I was promply told by my friends that was dumb and doing it would cost so much more money and blah blah blah to get the same sort of gains. Now the only reason in this conversation I mentioned destroking is because of the rediculiousness destroked supra engines are and a couple of supra owners who i know who have done it swear by it.

My questions to you are:1. What would you do, destroke it or just build what you got?2. What would be the pluses and minuses for each setup?3. Of course which one has the most potential?

[rmezz13]

By destroking you do mean less compression right?

If so, would you want to be running around with less compression and less power until you got the turbo?.... Turbo first then build the motor, then build the boost pressure. Make sense? Or do it all at once!

[TheHat]

yes but doing so also changes the displacement from 3.5 to 3.2. I would do it all at once if i did it. No point in having to pull the motor multiple times to get the job done.

My two friends seem to think the way to go would be turbo first. Which makes sence, then build the block and keeping the same displacement.

Either way turboing first then building the block or doing it all at once or building the block then turboing isnt the issue, the question is which would you all do if you were doing boost.

[sonsters]

with rmezz on this one, turbo 1st then block then up the boost.... ( dont know how use to power u are but for me putting on a turbo with low boost and gettin feel for it then upgrading block and internals and adding boost would b my way so i wouldnt get cocky and not know how to handle it and go in a ditch).... also (call me a D.A.) but why would u lower the compression and take away .3L? better turbo spool????

[rmezz13]

You should read the *stuck* post "how to do twins right the first time".

Also, consider punching out the block, then sleeving it for protection. You don't want to scar your block and have to buy a new one, would be easier and less costly to replace a sleeve.

-Sonsters-by reducing compression, you are relieving stress on the motor (so to speak) during boost, avoiding detonation and opening the door to higher boost options then go with stronger internals and then higher boost options, so on and so forth. If you are reducing the compression you mine as well use the strongest while your in there, for all the potential it will have for later on.

[sonsters]

ahhh i got ya... sounds complicated... iv never heard of destroking an engine.... cool to know tho thanks man

[TheHat]

When you destroke the motor you lower the compression to where it needs to be, allow the motor to be more rev happy. This in turn will get to that power that you find in the higher rpms faster, and if i'm not mistaken dont turbos like motors that spin fast? To me this make more sense then stroking it and having larger displacement to spin a pair of twins that can only get so big. Just a thought thats why I was asking what you all thought about destroking or just building the block as is.

[rmezz13]

My personal opinion is to build the heads first! This is what i plan to do this fall/winter, then next year sometime do turbo. With a head build (at least stage 2 cams) you will see significant increase in WHP (20-50 so i've heard) and it will open your RPM redline up to as high as 7500 rpm (from 6600 mines 04). With built heads, not only will it increase a lot of N/A power, but it will increase turbo power by opening up the RPM range. Higher rev = longer in boost = more power...... Just my philosophy on the idea.

If you are thinking of N/A build, i would recommend looking into building the heads first, that way you can change your mind to turbo if you won't and still have built heads, but if you build the whole thing N/A you would want to stroke the motor and increase compression, so you would be less likely to change to forced induction if you do the bottom end first.....

[rmezz13]

Don't forget to read the post *stuck* "how to do twins right the first time"

It mentions what compression ratio is best for this car with turbo(s) on it and what all to do as far as thermal coating goes. Pretty in depth write up. I learned from it.

[(NA)turalyRWD]

Hey everyone first post here but i just have to jump in and straighten you guys out. -To destroke a motor you need a crank with a smaller stroke-if you put it back together like this your compression would be pretty much usless as your pistons would stop short of the heads by whatever distance you destroked the motor.-to rectify this a destroker kit uses longer rods, and often uses pistons with the wrist pin moved closer to the top -this allows the longest rod possible to be used. and in a high revving application longer is good, As the revability of a motor is highly dependent on something called the rod ratio.-The rod ratio simply the length of the rod center to center divided by the stroke. as an FYI Formula one motors are up over 2. meaning the rods are twice as long as the stroke-You may ask what rod length has to do with anything, well it determines the amount of a angle the wrist pin will see and along with that the amount of side loading on the pistons, this is why long rod motors can get away with very mininal side skirts as they dont suffer as badly from piston slap.

Basically destroking is for high compression NA motors where the increased dwell ( time near top and bottom dead center) greatly improve pumping efficencies.

A stroked or well built stock displacement motor will spool a turbo faster and make more driveable torque at more usable RPM

Peace and Happy boostingGarrett

[evildky]

Hey everyone first post here but i just have to jump in and straighten you guys out. -To destroke a motor you need a crank with a smaller stroke-if you put it back together like this your compression would be pretty much usless as your pistons would stop short of the heads by whatever distance you destroked the motor.-to rectify this a destroker kit uses longer rods, and often uses pistons with the wrist pin moved closer to the top -this allows the longest rod possible to be used. and in a high revving application longer is good, As the revability of a motor is highly dependent on something called the rod ratio.-The rod ratio simply the length of the rod center to center divided by the stroke. as an FYI Formula one motors are up over 2. meaning the rods are twice as long as the stroke-You may ask what rod length has to do with anything, well it determines the amount of a angle the wrist pin will see and along with that the amount of side loading on the pistons, this is why long rod motors can get away with very mininal side skirts as they dont suffer as badly from piston slap.

Basically destroking is for high compression NA motors where the increased dwell ( time near top and bottom dead center) greatly improve pumping efficencies.

A stroked or well built stock displacement motor will spool a turbo faster and make more driveable torque at more usable RPM

Peace and Happy boostingGarrett

all correct, and you also slow down the piston speed, which reduces friction and heat

a bud build a short stroke L28, now has a powerband like a motorcycle

[rmezz13]

thanks for the schooling (NA)...... i learn something every time i get on this forum!

[TheHat]

sorry for not replying sooner but I have been with out a computer recently. All that tech stuff makes a great deal of sense but let me ask you this. If destroking is mainly for high compression N/A why then does titan destroke their high horse power turbo supras? Just curious. Granted they dont have they bottom end like most cars but their top end is leaps and bounds ahead of everyone else. Also wouldnt a car that is destroked and able to rev extremely high spool a turbo just as fast as somthing that revs a little lower and has greater displacement? Dont know too much about the turbo days of F1 but didnt they have setups like this?

[C-Kwik]

Destroking in some cases can reduce pistons speeds for a given RPM. This might allow higher revs (other engineering challenges overcome) which can increase a motor's leverage through torque multiplication. Motorcycles and F1 race cars are great examples of this. If high RPM operation were more practical, we'd probably see a lot more of it in passenger cars. But cruising around at 5-6K RPM at 60 MPH would generally not be very comfortable. Comfort is generally not the highest priority when building a race motor...

[BlackSmoke]

Ahh I was wondering if evil was on vacation. Knew he would come thru. (NA) like the mezz I learn alot on this forums I had no idea about. Nice poetry there.

[Soravia]

Sorry to bring out the thread again.

I'm currently doing a VQ30DE swap on one of my 240. I'm also planning to rebuild the extra KA after that and also rebuild ANOTHER VQ30DE afterwards.

I'm trying to see if I can destroke the KA and VQ, make the rods and crank lighter to decrease pumping loss and increase RPM (with stronger valve springs and valves)

How do I go about making the rods and crank ligher? I know people sell stronger and lighter rods, what about the crank? Grind off the metal and balance it afterwards?

[RCA]

I would stick with the VQ30.500cc per piston is the ideal displacement for an internal combustion engine.

Spending big bucks just to remove presious displacement sticks.Also if there is a FI future for you S13 then high revs is nice but torque FTW

[JETPILOT]

First you have to tell us what your goals are! How much power do you want to make?

I am making 565 whp with 93 octane on nothing more than a Greddy kit w/18G turbo's, Arias piston, Eagle rods, GTM cams, and a .020 overbore to clean up the cylinder walls. I could easilly make over 600whp just by upping the boost.

What problem are you trying to fix by de-stroking the motor. You have money to throw out?

The Greddy kit with the 20G turbo's Will make over 750whp on 93 octane.

No one is sleeving the VQ blocks anymore. All the sleeved built motors are failing. No oen really has figured out why yet, but they are all blowing head gaskets likely due to head lift.

No one is using 1/2" head studs anymore either as this is a likely contributor to the problem. Some people are now using the stock NISSAN head studs which are torque to yeild unlike the ARP.

My car makes power til 6700 rpm and I shift at 7000. All you need is a rev-up lower plenum to do that. You need mroe RPM than that?

What problem are you trying to solve here with destroking?

[Soravia]

I'm trying to make more HP, more torque per drop of gasoline. Power per liter of gas. I know that VQ makes more torque per liter than any Nissan engine running on NA. But VQ was made to go up to 4 liter (at that point it's not efficient). So my 3 liter engine is not making so much power for its heavy component.

I'm trying to make an engine with minimal powerloss on its own components. Aluminum drive shafts and flywheel would be put in, of course.

2.5L VQ25HR can go nearly 40MPG in a Skyline GT250. I want something like that. Fast and gas saving. Also having good amount of power at the top end to be used when needed. (I know that intake tuning counts a lot there)

What's the point of a fast car you don't drive because the gas cost as much as the car payment each month, right?

[RCA]

Can you explain what math you are using to come up with this conclusion?

Because I can see the logic in it. Also are you going N/A or FI?

[Soravia]

I want it just NA. There is no room for FI, the engine barely clears the steering rod.

My idea is that, the crank weights a TON on any engine and they weight more as the engines get bigger. Most cranks are there to take so much abuse (like 500WHP QR25DE with turbo). So on an NA engine, if I'm planning to make 250HP at most at top RPM, why should I have the engine rotating that crank for 500+HP? The combustion chamber has to push that crank everytime it fires.

I know that valve springs also saps the power but they are necessary for higher RPM operation. So I'm figuring lighter, longer and stronger rod and bearings for higher RPM, lighter crank for not losing the torque at higher RPM.

I've seen the thread on FreshAlloy for a NA KA24DE making 200HP at the crank. The thing dropped right after 5,500 RPM even though it made to 7,000 RPM.

Think of it as trying to make a V6 act like a Suzuki racing bike engine.

[JETPILOT]

I was answering the original question. I had no idea you too kit off topic.

Who's thread is this?

[RCA]

HMMMMWell in that case you are basicly looking for the most HP and use the least amount of fuel.

Well the reason why bikes get great milage is because they are .6L/ .75L/ 1L engines...

But yea the higher the RPMs the more HP. So so you want to take your 3.0L and turn it into a 2.5 or less...And if head work is done I can see your destroked VQ30 reving to 8.5k range.But they again a 3.L ont waste that much more gas...

The people who could answer you question the best IMO is the Engineering secion of NICO. They will tell you what to expect and if it is worth the investment.

I say...Make it a 3.5LThe 08 350z get 28mpg

[Soravia]

08 350Z's VQ35HR has the longer rod and stuff to make the drivetrain like I already described. It also have VVTL. but the crank is bigger (heavier?) than VQ35DE, etc. Still not an engine made for optimal power/gas.

[RCA]

Well I feel that the price of R&D and parts for this "most HP per MPG" will FAR out weight the MPG you will lose.

But definitly talk to the NICO EngineersThey're good.

I say...Make it a 3.5LThe 08 350z get 28mpg

Acually I ment Nissan NISMO 350Z and its 18/25

[JETPILOT]

08 350Z's VQ35HR has the longer rod and stuff to make the drivetrain like I already described. It also have VVTL. but the crank is bigger (heavier?) than VQ35DE, etc. Still not an engine made for optimal power/gas.

What exactly are you trying to do? Strap on a set of twin turbo's and call it a day! You want fuel economy get a Toyota Prius!

[TheHat]

sorry about the uber late reply on this but i am still going threw life without easy access to the internet and I feel bad going to the apple store and doing this.

Anyway my goals are a reliable 500 to 600 whp. Now I know I could get this with a simple bolt on kit and some other things, but I also want a motor that can rev to 10K or 11K and not loose any power doing in the process. When I say reliable I mean a car that I am not worried about being able to run when my women and I are leaving the Mall. Also keep in mind that I drift and I am looking to when the build is done going to the texas mile to hopefully have a street car that can run down a +200mph trap speed in a standing mile. So these are my goals.

My reasoning for doing debateing this build are that because I drift having a motor that has a nice linear power band that revs to 10 ro 11K would be nice for the look sweeping turns where my clipping point is behind me, I would have maximum torgue and hp because I could stay in my lower gears longer and I wouldnt feel like I was hurting my car like I do now when it bounces off the rev limiter. Also I am of the mind that you build the motor to do more then what you need it for that way it will run forever. Also doing the texas mile having a car that can rev really high especially in lower gears I would think maybe incorrectly I would beable to acheive a +200mph trap speed.

[bmike818]

[JETPILOT]

10-11K RPM

Titanium conencting rods $1000 ea.Titanium pistons $1000eaTitanium intake valves $100 eaInconel hollow sodium filled exhaust valves $150 eaTitanium springs and retainers $fill in the blank you get teh ideaCustom ground forged/balanced crankshaft $1500Intake manifold.... CJ Motorsports $3500Balalnce blue printing $xxx14:1 compression116 race gas all the timeFully worked Cosworth head castings $3000Custom dry sump oil system.... (stock oil pump can't handle over 8000 RPM. it will cavitate) $5000MOTEC engine managment $5000Darton sleeved block $1500

Shall I continue?

Armchair warriors!

[BlackSmoke]

JET sometimes you just need something funny, that was it today.+5