Stroker kit vs. stock crank with higher compression

[Oiluj]

I agree... HP doesn't really mean much with stroker motor. Torque is everything about how we drive these things while HP is just number that most of you are lying about anyway.

No need to lie about HP when you've got a dyno chart... Besides, most of us rarely, if ever, use all the HP our engines are capable of producing. I agree with you regarding torque. It's torque that makes a difference in everyday driveability and low end performance.

[doradox]

2).

What logic or physical laws can you use to make your point?

Steve

2)displacement.302 what?SBF?Or than minorly less a piece of crap 302 SBC?

3)400's were a pile of junk also.Comparing V-8s to L motors is a non-sequitur.

4)Brush up on your reading comprehension,

5)What part of can't be done don't you get?What works for a 2.8l will not(always) work for a 3.1.

6)DO i need to keep telling you that CI & HP increases are not LINEAR?

2) Just using your "numbers" argument. Chevy 302 by the way.

3) You said low rpm motors. I gave an example. It proved you wrong.

4) Cams don't stroke engines. Fact.

5) The part where you can't use logic or physical laws to make your point.

6) It seems you can't back up your claims with anything more than "because I said so".

That's unfortunate.

Steve

[doradox]

I have a two part question for our resident engine builders. Use the bore/stroke of an L28 for comparison.

First, is the power/torque gain for a fun-to-drive street/autocross powerplant with a full 3.0L stroker kit using 10:1 pistons worth the added expense compared to just using new 10:1 pistons and sticking with the L28 rods and crank?

Thanks, everyone.

Rebello 3.0 stroker kit with 88.5 bore (2.5mm over) gives 2982cc

stock 2.8 crank/rods with 88.5 bore (2.5mm over) gives 2907 cc

If you are looking to wind it out for max hp at high rpm the Rebello kit has the necessary robust crank and rods but the displacement gain is marginal at 2.5 % more than just boring the 2.8 to the same overbore as the Rebello kit.

For a fun to drive street car I'd overbore the 2.8 and spend $1900 minus the cost of pistons/rings on something else.

Steve

Edited October 6, 2010 by doradox
changed - to minus

[Z train]

2) Just using your "numbers" argument. Chevy 302 by the way.

3) You said low rpm motors. I gave an example. It proved you wrong.

4) Cams don't stroke engines. Fact.

5) The part where you can't use logic or physical laws to make your point.

6) It seems you can't back up your claims with anything more than "because I said so".

That's unfortunate.

Steve

Answer the question-is HP increase with CI displacement linear?

Mr Mortensen,answer your question,also.

[doradox]

2)

Wrong-Horse-power increase with displacement increase is NOT linear.

2)

DO i need to keep telling you that CI & HP increases are not LINEAR?

Answer the question-is HP increase with CI displacement linear?

I answered that in post 21.

And in the context of the exceeding small difference in displacement between the Rebllo 3.0 stroker and the 2.8 over bored the same as the Rebello kit it's even more valid.

But since you keep repeatedly making the claim why don't you put up or shut up?

Steve

[jmortensen]

Rebello seems to think that output is linear with displacement:

http://www.rebelloracing.com/enginebuild.htm

2.7 makes 270 hp

3.0 makes 300 hp

3.2 makes 320 hp

Coincidence??? BTW I believe that refutes the "answer" to the question which you've asked me.

SCCA seems to think that there is a linear relationship. At least they write their rules based on that assumption. There are probably 20 examples of this, but I'll give you the one that affects my car.

In X Prepared the formula for weight is as follows:

Minimum Weight Calculations

All listed weights are without driver. All weights are calculated

based on displacement as listed per Appendix A, 10.a. Example:

weight for a 1837cc RWD car is 1200 + (1.837 x 200) = 1567 lbs.

RWD: 1200 lbs + 200 lbs per liter

FWD: 1200 lbs + 150 lbs per liter

AWD: 1200 lbs + 250 lbs per liter

[Z train]

Rebello seems to think that output is linear with displacement:

http://www.rebelloracing.com/enginebuild.htm

2.7 makes 270 hp

3.0 makes 300 hp

3.2 makes 320 hp

Coincidence??? BTW I believe that refutes the "answer" to the question which you've asked me.

SCCA seems to think that there is a linear relationship. At least they write their rules based on that assumption. There are probably 20 examples of this, but I'll give you the one that affects my car.

In X Prepared the formula for weight is as follows:

Minimum Weight Calculations

All listed weights are without driver. All weights are calculated

based on displacement as listed per Appendix A, 10.a. Example:

weight for a 1837cc RWD car is 1200 + (1.837 x 200) = 1567 lbs.

RWD: 1200 lbs + 200 lbs per liter

FWD: 1200 lbs + 150 lbs per liter

AWD: 1200 lbs + 250 lbs per liter

Rebello's page in reference to his builds says the 3.0 motor CAN produce 320.

2.7 is limited by block parameters and exists SOLELY for guys who want their original blocks used.

3.0 you left out the oerative word-CAN produce.It can produce less or more.

The 3.2 produces 365hp not 320.

Nice cherry picking of facts.You must have voted for Obama.

And you still haven't answered the what the common thread was that permeated the three links you posted.

[jmortensen]

This is the most retarded argument I can recall having in a very long time. You can build an engine to make more hp, or more torque. You can push them to the limits, or build them more mildly. On the crazy side, Rebello built a 225 hp L16 for Dennis Hale. Does that prove that non-strokers make more power per liter? Or if we looked at old CP cars back in the day were pushing 350 hp out of an L24, does that prove that strokers suck? Is it coincidental that both of those all out race engines put out about 140 hp/liter? Again, built like for like, you're going to get a fairly linear return in hp for displacement. You can ignore that reality all you like, but I'm done trying to convince you of what is so plainly obvious.

[LeonV]

This guy is a troll, Jon. Leave him be in his own world...

[Pomorza]

This is the most retarded argument I can recall having in a very long time. You can build an engine to make more hp, or more torque. You can push them to the limits, or build them more mildly. On the crazy side, Rebello built a 225 hp L16 for Dennis Hale. Does that prove that non-strokers make more power per liter? Or if we looked at old CP cars back in the day were pushing 350 hp out of an L24, does that prove that strokers suck? Is it coincidental that both of those all out race engines put out about 140 hp/liter? Again, built like for like, you're going to get a fairly linear return in hp for displacement. You can ignore that reality all you like, but I'm done trying to convince you of what is so plainly obvious.

I'm saying this just for arguments sake. Power and displacement are never truly linear. Why this may look like it is, it has to do more with the amount of air and fuel being pushed into the "bigger" parts then the size of the actual bore. Example. I have an L28. If I was to stroke that out but leave everything else stock (cylinder head and fuel curve) I find it highly unlikely that I would get nearly as much power if I did what Z train did and added a better cam (which I assume would increase air influx) changed the fuel curve (in his case a better carb) and increased out flow (header).

We can argue about this day and night but what he says is true. If your going to update your motor you UPDATE your motor not just the block. That is pointless and a waste of time and money.

As you guys pointed out earlier a motor build is purely personal. If find having more than 250 hp in a Z unnecessary as they have plenty of it stock. But then again I know a friend of mine that had a 1000hp blown V8 his car. Its all preference.

Jan

[LeonV]

By the way, made a quick and dirty plot of hp vs. cc from data found here: http://www.simetric.co.uk/si_cc2hp_data.htm

I used only the passenger cars on the list, so Ford Fiesta through Honda Accord.

Plotting the displacement vs. hp you get the plot in the first attachment. The correlation is ok, but there are a couple of outliers as you can see. Taking out the two outliers from the data, you get the second plot. The data correlates a lot better.

Keep in mind, this is using a relatively small sample size. There is a lot of dependency on the way the engine is tuned. But generally, I think that you can surmise from the data that there is a pretty linear dependency of power on displacement.

I can go on and on, but it's a bit of a pointless argument at this point that has completely veered off topic...

correlation.doc

correlation2.doc

[jmortensen]

I'm saying this just for arguments sake. Power and displacement are never truly linear. Why this may look like it is, it has to do more with the amount of air and fuel being pushed into the "bigger" parts then the size of the actual bore. Example. I have an L28. If I was to stroke that out but leave everything else stock (cylinder head and fuel curve) I find it highly unlikely that I would get nearly as much power if I did what Z train did and added a better cam (which I assume would increase air influx) changed the fuel curve (in his case a better carb) and increased out flow (header).

Jan, did you look at his dyno plot? The motor that he showed the numbers for wasn't built for hp. It was built for torque. The hp peak is at 4430 rpm!!! It's no wonder that a stroker that has a low end cam and carb and exhaust to match puts out 50% more torque than a stock L20B. Why is this at all surprising??? Now if you put that same head/cam/induction system on an L20B, I suspect you would get other than stock numbers, and they would show much higher torque than stock. So his point that he got a 50% increase over a stock L20B really doesn't prove anything at all.

He's attributing the power gain to the bottom end exclusively. His results are not about the bottom end exclusively. His results are a result of BOTH a bottom end change and a top end change. If you change the bottom end, you can expect an increase of roughly the value of the displacement. If you change the top end, you can expect an increase based on how you change it. In his case he put a stump puller cam in and got an extremely torquey and low rpm motor.

We can argue about this day and night but what he says is true. If your going to update your motor you UPDATE your motor not just the block. That is pointless and a waste of time and money.

No, it really isn't true, and you're wrong about strokers. Adding the stroker "kit" that you can buy doesn't require anything other than the crank, rods, pistons, rings and bearings.

To emphasize the point made above about the top and bottom end having different results, what if you had this head on your L24?

http://forums.hybridz.org/index.php/topic/95308-bsr-gtu-e31-head-images/page__pid__898296#entry898296

If you built a stroker bottom end and put this head and induction on it, it would not be a waste of time. It would make more power with the stroker bottom end because of the increased displacement not because the stroker fairy would come by and waive a wand giving you more power.

There is of course a limit. If you take a tiny head and you put it on a bigger and bigger block, there is a point at which you'll get diminishing returns because the head simply can't flow enough for the displacement. I don't believe that you're getting there with ANY of the L series strokers I've seen with US market heads, whether it be a 2.3L L4 with an L16 head on it or a 3.2 liter with that BRE head on it.

Edited October 6, 2010 by jmortensen