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four stroke port /valve seat design

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Posted by: Pete Payne---------------------

Rich & all,
I am very interested in four stroke head design. You know, port geometry, seat angles, valve ratio's etc.. Are there any good books or other sources that help explain this? This info seems to be more guarded than all of the two stroke stuff. Also the Dynomation software seems to be good , and comes with a manual , I expect it to be geared toward operationg the software and not the actual design. Have you used this software and is it good? Any help would be much appreciated!
Thanks,
Pete


Posted by: bwalker---------------------

A good source for this type of info would be Dr. Gordon Blairs book "design and simulation of a four stroke engine"


Posted by: SFO---------------------

I have used desktop dyno with good results, ie actual hp figures within 2% of calculated #'s.
There is a good book about Weslake written by Clews(of ccm) that is good cylinder head reading too.
Is there a particular cylinder head that you are researching?
Superflow hosts a performance lecture that is bitchin'.
Also The Performance Racing Industry magazine has a trade show that will feature many top cam designers and head manufacturers that lecture and reveal their ideas.
If there is a certain head you are working with maybe someone can reveal tricks with it.
This forum is an excellent place to be edified.
Rich is very deliberate in the facts that are posted here.


Posted by: Rich Rohrich---------------------

Pete - Ben and Bill (SFO) have probably tossed up the best info. There really isn't a whole lot of info out there. I think this is partly because great airflow guys tend to be rather odd recluse types, (Kenny Augustine and Axtell come immediately to mind ) and partly because in the past it was a lot more ART than SCIENCE. If you can track down old copies of Circle Track, a couple of years back Smokey Yunick (my hero) wrote a two-part feature article on airflow in engines that was great. As Ben pointed out Blair's book is outstanding but strap in cause it's a college course in engine design. Great info if your brain doesn't explode (Mine has certainly had it's share of blowouts from that book )

Like Bill pointed out Desktop Dyno is a good tool because it contains some of the basic math from Dynomation. If cost isn't an issue Dynomation is a great tool for building paper engines and eliminating a lot of bad choices. It's especially helpful for looking at pipe/cam combos. Well worth the price.

In the end, a flow bench a ton of time a ton of cash to pay for all the heads you'll wreck and maybe a dyno is the best way to learn the art and science of cylinder heads. I've had a flow bench for about 20 years and the only thing I'm SURE of is air rarely does what we think it will.

Good luck. It's a LONG bumpy road but it's a fun journey.


Posted by: Pete Payne---------------------

IRich, Ben , & Bill,
Thanks for all the great info. I should have known that Gordon Blair had a great book. My brain has also exploded because of his two stroke book, and using the SF-110 on two strokes. I have been recieving the Performance racing industry magazines and there is alot of great equipment in there , and I would like to go to the trade show one day.
In my area there used to be a guy that built cylinder heads for the Toyota mid atlantic race cars. If I remember right they used a 4-cylinder ford mustang engine. As Rich stated this guy was a little different. He had all of the cool equipment , you know the serdi 1.0 cylinder hear machine $$$$$
but I only saw it in action one time. The guy was very secrative. I could not get much info out of him.

There are actualy two cylinder heads that I am working on now, the 96 Honda CBR 900rr and aSuzuki 94 DR 350 off road model. I would like to here if any of you guys have ever tuned on one of these cylinder heads.The CBR has 1mm oversize valves from kibblewhite and the dr is all stock.

I understand that Smokey Yunick was the man that started it all
How about this Mondello guy? I here he has a school that teaches four stroke porting. I will also contact superflo and see about there seminars. Thanks for all the help--Pete.


Posted by: Rich Rohrich---------------------

Pete - Superflow makes the previous years performance seminars available on audiotape.

The DR350 is really a horrible ( by japanese standards) cylinder head stock. The ports are OK but the port ot valve insert transition is miserable. I always start by filling in the gaps on the intake side with aluminum based epoxy and trying to grind a cleaner transition. They can be made to work, and it's a good head to learn on because it's one where getting the valve seat right makes all the difference in the world. Increasing the short side radius with epoxy on the floor can also be useful, but it depends a lot on what you end up with at the port throat.

Most of the new engines are tough to improve upon once you get past cleaning up the production machining flaws. Castings are getting better, and they can't afford to throw away performance in the new high-rpm engines so they come from the factory in pretty good shape.


Posted by: David Trustrum---------------------

Another good read is Kevin Cameron’s Sportbike Performance. It is easy to digest for a starting course.

Blair is on another planet. Probably a good planet if you can speak the language.

PS Had heard that the CBR production tolerances were a bit suss which is why there is a huooge difference in performance between one bike & the next. Some theorised that cam/valvetrain machining was at fault.


Posted by: cujet---------------------

Hey Rich, A few years ago I was involved in the modification of various cylinder heads. The goal was to convert Ford 1600-1800cc BD DOHC 4 valve series engines to tunnel port designs. The stock intake ports were similar to current motorcycle engines. WIth a HP ceiling of about 250-280 and VE of 107% the intake ports were the logical place to improve flow and increase RPM capability. The change to tunnel ports was very time consuming, as the work was done by hand. These engines were 400-450cc per cylinder. We were able to extract about 75HP per cylinder!

My point is that even engines such as the Yamaha 4 strokes may have room for improvement. Yes, the changes might be beyond the scope of reality for most. However I still believe that more HP is available.

Chris


Posted by: Rich Rohrich---------------------

Quote:
Originally posted by cujet
My point is that even engines such as the Yamaha 4 strokes may have room for improvement. Yes, the changes might be beyond the scope of reality for most. However I still believe that more HP is available.


No question that there is always room for improvement. Finding a good balance between cost versus benefit just gets trickier as the stock specific output gets higher.


Posted by: SFO---------------------

Pete, I just received the catalog from these guys...

http://www.newen.com/about/about.htm



It has the serdi style cutting tools with all the profiles available.
You can also get custom profiles.
I am looking at the serdi 1.1 for my shop. If you need some help email me.
Bill



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