ESE's works engine tuner

[bucketracer]

And a little boy waits .......

I understand TeeZee has had all sorts of trouble trying to get his first triple port effort to run properly with a carb before he can try it with EFI, and it looks like he will flag it and start again.

Apparently taking a perfectly good 200 deg duration single exhaust port cylinder and adding side ports has not worked out very well. Looks like you can have to much exhaust blow down STA or at least get out of balance with the other aspects of the cylinder.

The word is that he is going to prepare a proven single exhaust port cylinder that has worked well with before for EFI and try again. Then have another go at making another triple port, with about 188 deg duration and only slightly more blow down STA than the 200 duration single port had.

[wobbly]

I dont get it - take a perfectly good single port with 200* and add triples - of course its going to have idiot blowdown STA.
Then drop a triple port to 188*, and of course it wont have enough, I thought we were using EngMod to stop all the guessing bullshit.

[TZ350]

I dont get it - take a perfectly good single port with 200* and add triples - of course its going to have idiot blowdown STA.

I had cut the side ports into the 200 when blow down was all the rage and before I had my own copy of EngMod2T.

When I made the triple exhaust port cylinder I was aiming for the maximum blow down STA possible. 200 deg worked well for me on the single exhaust port cylinder so I figured it would be even better with side exhaust port windows. I wish I had of had the EngMod2T simulation package before I made the triple port cylinder.

You will have to go to the original post to see the simulated and dyno graphs.

Then drop a triple port to 188*, and of course it wont have enough, I thought we were using EngMod to stop all the guessing bullshit.

As if I would have just guessed at 188 and not simulated some options. ...

Still, I will post pictures of the STA's and Graphs later as there is something I dont understand. Matched STA's did not give the best graph, I got the graph I liked best with 188.

[FastFred]

I dont get it - I thought we were using EngMod to stop all the guessing bullshit.

Bit silly suggesting TZ just flounders around guessing. Sure he often gets it wrong but he probably does more research than most and is indisputably at the pointy end of the Bucket horse power stakes.

[F5 Dave]

So how big do you think you can make these aux without encroaching the wrist pin yet have transfer area for revs you're turning? I don't have engmod but you're suggesting quite a lot less degrees than say the RSA

[2T Institute]

I had cut the side ports into the 200 when blow down was all the rage and before I had my own copy of EngMod2T.



You will have to go to the original post to see the simulated and dyno graphs.



As if I would have just guessed at 188 and not simulated some options. ...

Still, I will post pictures of the STA's and Graphs later as there is something I dont understand. Matched STA's did not give the best graph, I got the graph I liked best with 188.

Your possibly looking at even more basic issues, I still see the rear transfers pointing at the exhaust duct and square subs. The subs should be triangular with a dead straight top edge extending to just before the centreline of the crank/bore. That works better than anything else.

[husaberg]

Your possibly looking at even more basic issues, I still see the rear transfers pointing at the exhaust duct and square subs. The subs should be triangular with a dead straight top edge extending to just before the centreline of the crank/bore. That works better than anything else.

I guess you mean something like this?

[wobbly]

The issue you are up against TeeZee is that EngMod has no way of knowing how bad your transfer duct ans scavenging pattern really are.
The ducts you have and the port geometry ( mains too big ) means the transfers as modelled are not, and cant, perform anything like the simple one dimensional numbers suggest.
Thus you have to use the blowdown to shoot for the actual power you need, and the transfers MUST be way bigger in STA than the calculations suggest.
And in doing this, the Ex port STA number is basically irrelevant.
But in any case of trying to extract any worthwhile power out of a race engine worthy of being called one, it is near on impossible to generate sufficient REAL transfer STA, then add the correct Blow STA on top of this
- with a limiting total height at 188*.
It just cant be done.
The ONLY thing 188 has going for it is strong port/pipe resonance over a wider band, but no matter what you do the power achieved will always be severely limited, even with the best developed ducts and ports known to man,
completely what you havnt got due to the inherent design limitations of the base engine.
Not arseholing your efforts at all - just pointing out hard learned basics of the physics,gained from fucking it up myself.

[Frits Overmars]

I agree 100% ,Wob.

[TZ350]

So a little guessing really is involved ....

The issue you are up against TeeZee is that EngMod has no way of knowing how bad your transfer duct ans scavenging pattern really are. The ducts you have and the port geometry ( mains too big ) means the transfers as modeled are not, and cant, perform anything like the simple one dimensional numbers suggest.

I also used the worst transfer duct option available.

Thus you have to use the blow down to shoot for the actual power you need, and the transfers MUST be way bigger in STA than the calculations suggest. And in doing this, the Ex port STA number is basically irrelevant.

Wob, I suspected this, and its nice to have it confirmed as its the way I had already approached it.



With the spread of the STA's for the 188 duration triple Ex port are pretty much the way you outlined they should be.

But, after what you have said, maybe I need to go even bigger on the transfers STA, so your input here with some concrete numbers would be welcome.

The ONLY thing 188 has going for it is strong port/pipe resonance over a wider band,

A wider spread is what I was looking for and the approach was pretty much the way you outlined it should be.

So your best guess's at how much I should favor the transfer ports and any of the other compromises needed for EngMod2T to better model my motor would be welcome, what do you think?

[TZ350]

I still see the rear transfers pointing at the exhaust duct and square subs.

Its the same cylinder re cycled for the EFI experiment.

The subs should be triangular with a dead straight top edge extending to just before the centreline of the crank/bore. That works better than anything else.

Thanks for the tip, its the shape I will aim for on the next cylinder.

[speedpro]

With talk of building up the exhaust port floor I thought it interesting that the transfer ports have a figure that can be entered for when they are fully open in crankshaft degrees from TDC. There would obviously be flow benefits having the port fully open and unobscured for the maximum number of crankshaft degrees but I wonder what the effect of reducing the ultimate port area would be.

[TZ350]

So how big do you think you can make these aux without encroaching the wrist pin yet have transfer area for revs you're turning? I don't have engmod but you're suggesting quite a lot less degrees than say the RSA

After quite a bit of work, I have just figured out, that I can plan, simulate and maybe even cut ports the size of the RSA but with constipated transfers and other real life short comings, having blow down like an RSA won't do me any good.

Something less that the rest of the motor can keep up with will suit me better. Pretty obvious really....

[tdc211]

My 31.8hp graph back around page 682 is all about transfer and scavenging . I have more transfer timing than most and is a triple ex setup.
Engine did not have any bmep in the mid range until this was done. Also it is the reason it makes pk power at 11000 with higher ports than 188, as I sacrificed some blowdown time/area . I built another one and am at 33.3hp at 12000rpm. I am working on more hp at higher rpm with the same bmep. I lost a little bmep, but not terrible. Working on getting that back now. Wob is correct as always.

[FastFred]

I have been following this thread. Here is my output shaft steel wheel dyno chart of my mx piped engine, a few ccs over 100.

Save looking for it.

BMEP close to 12 Bar, not a bad effort.