R&D help: shorten engine stroke

[1997supraman]

Hey guys I am new here and could not find any other place to ask this so here goes.
To me nothing compares to F1 technology and it has inspired me in the area of R&D. You see not too long ago in another forum there was this guy posting his results from applying some common F1 tech to his car, Toyota Supra. If I remember correctly he applied the science of titanium connecting rods, lightened flywheel, lightened crankshaft, custome oiling system, dry sump, and a few other things. Then he posted this video http://www.youtube.com/watch?v=lch_exQJPzc

The change in sound and performance was amazing with these changes as you can see and all his R&D led me to ask; what changes must be made to an engine if you plan on shortening the stroke in an engine?

Thanks

Mark

[alexbarwell]

Welcome, not really a 'just' job though. Bit of a mix of things to find the optimum, but would say a shorter throw on the crank which could involve starting from scratch on that. Your swept distance per bore is reduced so likewise is volume requiring an increase in bore to return to the same swept volume. The pistons are no longer travelling up as far, so to maintain CR either high crown pistons, planed head and/or block could be considered. Large bore short stroke give an over-square engine tending to be very revvy, but bringing the power band up the range, high revs would suggest lighter internals due to the increased rate of thrashing around and kinetic enrgy increasing with the square of velocity. To make the most of this, improved breathing is required which sees you going to town on the head, inlets, exhaust....
Where to stop really.
BTW, hope he did his brakes as well

[Ciro Pabón]

Well, people has been stroking engines since dragsters appeared, so there is plenty of info about it. Unlike boring the cylinders, you get a significative increase in displacement. There are plenty of kits used mainly when rebuilding an engine.

Where I live it's very popular to take a 350 cu. in. Chevy engine and use a 400 cu. in. crankshaft: you get a 383 cu. in. displacement. That is a huge increase in displacement, compared with re-boring the engine, at a marginal price.

If you use stock rods, the piston pin must be raised (i.e., the compression height reduced) by the same amount as half the increase in stroke.

I've also seen many people using 6 inch rods instead of the 5.7 original Chevy ones.

The rods sit on the crank pins: it is clear that the new crank pins have to match the rods that you use. Pistons have to have shorter skirts, for the pistons not hitting the counterweights, nor going over the ends of the cylinders.



You have to check that (at least in V-8 engines) the clearance between the camshaft and the rods is enough, like this:



I know you can get aftermarket blocks with raised camshafts, in that case you'll need longer timing chains and shorter pushrods.

The pan rails need to have enough clearance. There are also aftermarket blocks with wider pan rails and extra crank-clearance scallops.

You'll normally increase piston speed. This means that sometimes you have to turn down the redline.

Please, take in account that all this I have seen done, but I've never done it: I haven't touched my Pontiac Goat. I've rebuilt it three times, but I intend to have an "antique and classic" license plate some day. I've only adapted it to natural gas, that's it. Even the radio is original... and the brakes still have drums. Do not brake suddenly in front of me when raining, because my right knee hurts.

[majicmeow]

Keep in mind, that Supra probably has a $30000+ engine in it. Although getting the 2JZGTE to produce large BHP numbers reliably is fairly "simple", 1187 RWHP is not.

A stock unopened 2JZ will easily produce up to 800 RWHP with no bottom end modifications. Any 2JZ producing MORE than 900 RWHP will generally have a 3.2 to a 3.5L stroker kit which INCREASES the stroke and bore sizes to their maximum on that engine.

Along with a fully built bottom end, HUGE turbo, massive cylinder head work and countless other mechanical modifications, the MOST significant thing needed in the life of a 800RWHP 2JZ is a properly tuned engine management.

I've seen countless 2JZGTE's blow up at 500HP levels because of a bad tune (ie: piggy back, mega-squirt etc..), while I've also seen a few (2 or 3) of the 1000+ HP cars run all day long, 365 days a year because of proper engine management tuning techniques (AEM, HKS V-Pro etc tuned by a professional)

Chances are, the supra in that video is NOT running 10500RPM... the 2JZ is a HP/TQ monger engine and is NOT rev happy. I'd say 9000RPM max, but that's just in my experience.

my 2¢

[alexbarwell]

These strokers mentioned above are using crankshafts with longer throws, so to go for short stroke requires the reverse action, but again changing piston crown height in compensation. By my understanding longstroke is for torque at the expense of revs, and shortstroke is revs and hp at the expense of torque. So re-engineering for a short stroke/throw crank, but not involving some of the other tricks seems a bit of a halfway move. Watch out for using shorter stroke rods with a longer stroke crank as the angle the rod has to turn through is greater and can end up developing additional side loads to the bore and bearing journals on the power and compression strokes increasing bore and journal wear - maybe OK for a short-lived race engine but not clever for a hot road car unless you are pulling it apart regularly.

[Ciro Pabón]

Oops. Thanks Alex, I guess I have to think before answering. All I mentioned was for dragsters.

In that case, as it has been pointed, you have to use good rings, improve the breathing and shorten the rear end gears a bit, because you're losing torque at low revs. You might look into improving the cooling and oiling systems, because the engine will tend to overheat. You could use a different fuel, because you're changing compression ratio. If you're using your car in the streets, you might check emmisions, because they will be worse and maybe fuel economy will be lower.

[donskar]

Keep in mind, that Supra probably has a $30000+ engine in it. Although getting the 2JZGTE to produce large BHP numbers reliably is fairly "simple", 1187 RWHP is not.

A stock unopened 2JZ will easily produce up to 800 RWHP with no bottom end modifications. Any 2JZ producing MORE than 900 RWHP will generally have a 3.2 to a 3.5L stroker kit which INCREASES the stroke and bore sizes to their maximum on that engine.

Along with a fully built bottom end, HUGE turbo, massive cylinder head work and countless other mechanical modifications, the MOST significant thing needed in the life of a 800RWHP 2JZ is a properly tuned engine management.

I've seen countless 2JZGTE's blow up at 500HP levels because of a bad tune (ie: piggy back, mega-squirt etc..), while I've also seen a few (2 or 3) of the 1000+ HP cars run all day long, 365 days a year because of proper engine management tuning techniques (AEM, HKS V-Pro etc tuned by a professional)

Chances are, the supra in that video is NOT running 10500RPM... the 2JZ is a HP/TQ monger engine and is NOT rev happy. I'd say 9000RPM max, but that's just in my experience.

my 2¢

A local Houston tuner (SGP Racing http://www.sgpracing.com/) built a Supra engine that produced 1500+ HP . Not sure how LONG it lasted though . . .

[1997supraman]

There are some 3.0 Supras producing more than 1000 rwhp realiably. Reputable tuners will expect these to last I know someone with a 1000rwhp Supra who abused the car with highway pulls, dynos, antilag, and even 1/4 mile runs no problems. There are a lot of great tuners out there with 1500 RWHP beast no problems at all. As a matter of fact Boostlogic just managed to go 241 mph in the texas standing mile. I REPEAT 241 MPH IN THE STANDING MILE. How fast and reliable this car is well in the standing mile the Bugatti Veyron managed to barely get to the 200mph.

These cars are very reliable or else they would not have such a fierce reputation.

And another thing, Plenty of built Supra are regularly revving past 10000 rpm no problem at all. The one in the video posted sounds unique because of the modifications made.

Keep in mind, that Supra probably has a $30000+ engine in it. Although getting the 2JZGTE to produce large BHP numbers reliably is fairly "simple", 1187 RWHP is not.

A stock unopened 2JZ will easily produce up to 800 RWHP with no bottom end modifications. Any 2JZ producing MORE than 900 RWHP will generally have a 3.2 to a 3.5L stroker kit which INCREASES the stroke and bore sizes to their maximum on that engine.

Along with a fully built bottom end, HUGE turbo, massive cylinder head work and countless other mechanical modifications, the MOST significant thing needed in the life of a 800RWHP 2JZ is a properly tuned engine management.

I've seen countless 2JZGTE's blow up at 500HP levels because of a bad tune (ie: piggy back, mega-squirt etc..), while I've also seen a few (2 or 3) of the 1000+ HP cars run all day long, 365 days a year because of proper engine management tuning techniques (AEM, HKS V-Pro etc tuned by a professional)

Chances are, the supra in that video is NOT running 10500RPM... the 2JZ is a HP/TQ monger engine and is NOT rev happy. I'd say 9000RPM max, but that's just in my experience.

my 2¢

[riff_raff]

To shorten the stroke of an existing engine, at a minimum you will need:

1) a new crank with a shorter throw.
2) new longer rods; or new pistons with a taller deck; or a block with a lower deck height; or some combination of these three.

Beyond these minimum requirements, you will need to upgrade or modify almost every other engine part to maximize the potential of the shorter stroke. And typically, these costs go up at something like the fourth power of the RPM increase you seek to achieve ($=deltaRPM^4). I believe this exponential mathematical relationship between dollars and engine rev's is sometimes referred to as the Ecclestone equation.

[Belatti]

I believe this exponential mathematical relationship between dollars and engine rev's is sometimes referred to as the Ecclestone equation.

[n smikle]

to what order of shortening are we talking about here? 5mm?

[donskar]

I believe this exponential mathematical relationship between dollars and engine rev's is sometimes referred to as the Ecclestone equation.

Now THAT is good technical discussion!

[Conceptual]

I believe this exponential mathematical relationship between dollars and engine rev's is sometimes referred to as the Ecclestone equation.

Now THAT is good technical discussion!

HERE:HERE

[alexbarwell]

Once again, it depends on what your plan is for the engine. Depends on the initial properties of the engine, how far you are (planning on) going etc. The fact that you are considering shortening the stroke means you are heading down a certain route already. Firstly, what stock rods, cranks, heads and pistons are there, then mod options on any number of these. Asking how much to shorten by is very much like asking 'how long is a piece of string'. Not sure how well this translates for some of you guys. And before someone asks, no I don't think it makes much difference going metric or imperial, just as long as you pick ONE.