Stroking (Not that kind, sicko)

[fieroturbo]

Hey, a little question.

I want to stroke my 2.5 Pontiac Iron Duke 4 banger from my Fiero, and it's going to go from 3" to 3.625", or 2.5 to 3.0 Liters.

When you stroke an engine, is it the crank that is different, or the rods?

I don't want to sound like an idiot when I call KRP and order the parts needed.

[ivymike1031]

Usually both - the crank determines the stroke all by itself, but the conrods&pistons have to add up to give you the right compression ratio, TDC clearance, etc.

[fieroturbo]

Well, I want to keep the compression down (I know, you think I'm crazy now, don't ya?) I want to turbocharge the thing, cause the compression ratio is already at a low 8.3, which is perfect. But I'm hoping I can keep it that low and still get more C.I. The lower the ratio=the more gases that come out the exhaust=better turbo performance.

I'm probbably not going to get it as soon as I wanted to though. I was going to get it at the end of this summer, but Garrett is taking their good sweet time with that electric motor spooling turbo.

Yes, that's right, electric motor on a turbo. No 4-cyl lag. Audi is going to be the first company to get it for their 1.8's. Then aftermarket parts companies will follow shortly. But I haven't seen any new news, so I'm assuming it's kaput. Oh well, I'll just have to ceramic coat a T4 to kill the lag.

I'm gonna go all out on reliability, cause I found out there's now a Venom nitro kit for chevy s-10's with the same engine I have.

So I'm ceramic coating whatever I can, I'm micro-coating whatever I can (it's a new permanent lube that reduces friction, but can be removed with WD-40), I'm getting forged everything, computerized cylinder honing, stainless valves, the works.

I'm thinking after all of this, I'll up the redline from 5800RPM to somewhere between 6500 to 8000 RPM. I did some computer dyno sims, and the power curve falls off at 6400 with the OHV. But with the DOHC (which is no longer available), the horses and torque are strong till 7700RPM, with 8000 as the redline.

Thing is, I only have 52K on the thing. So I hope it blows sometime this century so I have a reason to rip it apart. I'll just blow my $ on the handling and brake upgrades.

Thanks!

[ivymike1031]

Originally posted by fieroturbo
[b]Well, I want to keep the compression down (I know, you think I'm crazy now, don't ya?) I want to turbocharge the thing, cause the compression ratio is already at a low 8.3, which is perfect. But I'm hoping I can keep it that low and still get more C.I. The lower the ratio=the more gases that come out the exhaust=better turbo performance.

Compression ignition? Charge induction? Are you suggesting that you want to increase boost pressure and keep the peak cyl pressure low? Otherwise I'm not sure what you're trying to say...

So I'm ceramic coating whatever I can, I'm micro-coating whatever I can (it's a new permanent lube that reduces friction, but can be removed with WD-40)

What components are you putting this "micro-coating" on? Are you saying that it washes off w/ WD-40, but not with gasoline or motor oil?

I'm thinking after all of this, I'll up the redline from 5800RPM to somewhere between 6500 to 8000 RPM. I did some computer dyno sims, and the power curve falls off at 6400 with the OHV. But with the DOHC (which is no longer available), the horses and torque are strong till 7700RPM, with 8000 as the redline.

You don't seem to have mentioned anything that will actually help your engine run safely at higher speeds... What have I missed?

[SaabJohan]

Another way is to don't stroke it and use higher revs instead, a short stroked engine can rev higher.

Also, use as long conrods as possible, if necessary use pistons with lower compression height.

Even with an electric motor on the turbo there will be lag, if you got no lag you got no turbo.

To use as low compression as possible isn't the best thing to do since the engines effiency will decrease.
Even high boost, high power modern turboengines have high compression ratios, high 8 och low 9 can be used with around 3 bar boost pressure.

And it's lower compression = more exhaust per crank horsepower.

[fieroturbo]

Look, I've read the books and magazines on turbos, and lower compression ratio (along with a better exhaust system) means the turbo will be much more efficient.

And yes, micro-coating can't be harmed by gasoline or motor oil. I don't know why, I didn't invent it, some ceramic coating company did, I'll give you the address when I get back from the west coast on Thursday. And I'll be micro coating my crank, con. rods, cam, lifters, rockers, (I think the lower portion of the pistons can be coated too).

And the stroker kit comes only with top quality con. rods, crank, and pistons, I think it's TRW Forged, and shot peened, I don't know off the top of my head, but they tested it, and it can go to 8000RPM, or maybe even higher. I'll ask. NASCAR uses it (Daytona Dash Series).

Now I understand what you're saying with just raising the redline, but I've done the dyno tests, and so have a bunch of NASCAR teams, and the power band is way to low above 6000RPM's with my cylinder head and the 3" stroke. If I go with the larger stroke, the engine responds in the mid range mostly, and somewhat in the high end. It is a truck engine saddly, in its stock form.

But once a few mods are done (like stroking it and then raising the redline), the HP goes above the Torque at 5200RPM, and Stays above 200HP untill 7800RPM.

It's 246HP at 6000RPM and 271Lbs/Ft. TQ at 3500-4000RPM, in a N/A OHV 4 Cylinder.

I'll play with the cam settings and exhaust setups to alter the high end stuff when I get back from Cali and Nevada.

quote: Even with an electric motor on the turbo there will be lag, if you got no lag you got no turbo.

I'll say again. WITH THE ELECTRIC MOTOR SPOOLING THE TURBO TILL THE GASSES BUILD UP ENOUGH, THERE IS NO LAG!!! Just like how V8's have instantaneous turbo boost because there is so much exhaust output, resulting in no lag.

I don't understand what you mean "if you got no lag you got no turbo."

What, is turbo lag suddenly a family tradition or something? Just cause you have turbo, does not mean you have a 1 to 2 second lag like all of those small buzzy little hondas out there.

Instantaneous turbocharging is possible, and it has been proven time, and time again in the V8, and even in the V6 world. Want proof? I'll scan the cover of this months engine builder's magazine issue.

("I see," said the blind man, to the deaf woman who said, "I hear ya.")

And, yes, lower compression means more exhaust gas PER CRANK HP (happy now?), WHICH MEANS QUICKER TURBO SPOOLING, WHICH MEANS BETTER TURBO EFFICIENCY, WHICH MEANS MORE BOOST IS POSSIBLE. RIGHT??????!!!!???? (I'm using logic here, try it sometime).

Talk to ya Thurs.

[SaabJohan]

But compression ratio affects more than just the turbo, there is throttle respons, fuel economy, hp / boost... and that can make the spool up slower instead of faster with a lower compression.

Lag is affected by many factors, since you already have mention exhaust gas, there is easy to figure out that the engine rpm, volume and VE also affect lag.
The turbo itself is also important, turbine effiency, cruise speed, speed at boost, inertial mass of turbine, axle and compressor wheel.

Yes, you can shorten the lag by adding extra power by an electric motor, but only reduce - not eliminate.

When changing pistons, crankshaft and conrods, the cumbustion chamber will be affected, this means that you must get the quench area, squish zones and so on right.

A good turboengine exhaustsystem is no exhaustsystem!

And I've read books about engines, turboengines, fuels, radial turbines, centrifugal compressors, injection systems and I've also written a 50 page essay in the subject.

[Gonthrax]

Now I can't speak on the rest of this, but I will talk about turbo lag.

I don't know what this deal your talking about is but I am sure it won't work like it sounds like it will. Does this moter keep it spinning all the time? If so, say buh bye to your fuel economy (along with that low comp ration ) If the moter starts turning it at some predetermined situation, you will still lag because the moter has to spool it up. It takes a few seconds to start spinning at 100k+ RPM
If you want to reduce lag instead of spending the huge amounts of money I'm sure this thing costs, just do this. Port and polish your head, go with a smaller AR, perhaps 45-50 (which will give you a tad of torque while off boost anyway ) Find some cam gears that work well with a turbo. With all this you should find yourself spooling atleast 1000rpm sooner and comming on full boost around the same amount earlier.

[ivymike1031]

Originally posted by fieroturbo
Now I understand what you're saying with just raising the redline, but I've done the dyno tests, and so have a bunch of NASCAR teams, and the power band is way to low above 6000RPM's with my cylinder head and the 3" stroke. If I go with the larger stroke, the engine responds in the mid range mostly, and somewhat in the high end. It is a truck engine saddly, in its stock form.

2 things come to mind:

1) you keep talking about "computer dyno simulations," and I hope that's not what you're referring to now when you say that you've "done the dyno tests." It's not a TEST unless you've run hard parts in that configuration. Without running hard parts, the best you could have done would be a representative simulation... but even the $200,000 packages aren't truly representative simulations at this point in time. I'm guessing that you've really been using a "table look-up" or "curve-fit" type of program, rather than a true simulation, and I'm very skeptical about the quality of results that you'd get from a program like that (especially if it's sold for $45 at the local auto parts store). If you're only looking for a +/- 15% accuracy, you might be able to get it from such a program if you don't run it too far out from where the table data ends. It'd probably be even more accurate than that as long as you stayed "on the table," but some of the numbers you've thrown out just don't seem to fit (didn't you say that the program predicts that a small-displacement n/a V6 engine can put out 275HP as built, but jumps to 500HP after break-in?) Sounds fishy to me.

2) Increasing stroke usually reduces the peak operating speed for an engine, and often reduces the rpm at which you find peak HP and peak torque.

[SaabJohan]

An electric motor is supposed to help the turbocharger to during the spool up. I heard about this a couple of years ago but since then there have been quiet about it. Maybe because a VNT turbo can do it much better with less problems. Today the VNT turbos have problems with the hot exhaust from gasoline engines but we can hope it will be solved soon - it would be nice to have a turbo that is both small and large when it needs to be.

[Gonthrax]

Originally posted by SaabJohan
An electric motor is supposed to help the turbocharger to during the spool up. I heard about this a couple of years ago but since then there have been quiet about it. Maybe because a VNT turbo can do it much better with less problems. Today the VNT turbos have problems with the hot exhaust from gasoline engines but we can hope it will be solved soon - it would be nice to have a turbo that is both small and large when it needs to be.

Adjusting AR ratio, there's an idea