Who is best for cylinderhead development work uk
Discussion
Back in the day, when engines were designed on drawing boards, the "ports" ended up just being holes to the outside. They were designed, just attempted to avoid the major stuff in the way (head bolts, waterways, lifter buckets, valve stems etc). Production (ie volume) casting and machining was shockingly poorely controlled (hand rubbed sand cores from balsa wood tools, single angle valve seats, fitted with a hammer etc). Back then, you could make significant improvements to flow, because the original port and chamber were so bad. Engines wheezed along at 60 to 75 bhp / litre at a low rpm, so with hand finishing, you could gain at least 25% more power and probably even more if you put the time and effort in.
Fast forward to any engine made in the last 15 years, and it's a different world. Ports are optimised in the virtual world well before they ever get "designed" into a real cylinder head. Then millions of ££ of development and production engineering are thrown at it, Modern N/A engines, like the BMW M3 engine make 100bhp/litre in factory tune, and already rev to nearly 8krpm.
So, even if you're going to spend another million on the combustion system, chances are, you are going to struggle to find as little as 5% more. If you want 10% more (which is just 30 bhp on a 300bhp engine) then you're going to have to pretty much build a custom billet engine that can rev to 9k to leverage any increased port flow etc
So, why are you building this engine? if it's a true racing engine (you are trying to win something) then yes every last horse counts, but for a road or trackday engine, why bother? (money would be better spent on better EMS and mapping, or better brakes etc)
Fast forward to any engine made in the last 15 years, and it's a different world. Ports are optimised in the virtual world well before they ever get "designed" into a real cylinder head. Then millions of ££ of development and production engineering are thrown at it, Modern N/A engines, like the BMW M3 engine make 100bhp/litre in factory tune, and already rev to nearly 8krpm.
So, even if you're going to spend another million on the combustion system, chances are, you are going to struggle to find as little as 5% more. If you want 10% more (which is just 30 bhp on a 300bhp engine) then you're going to have to pretty much build a custom billet engine that can rev to 9k to leverage any increased port flow etc
So, why are you building this engine? if it's a true racing engine (you are trying to win something) then yes every last horse counts, but for a road or trackday engine, why bother? (money would be better spent on better EMS and mapping, or better brakes etc)
Mignon said:
Johnny Middleton at Competition Engine Services. Happy days. Johnny taught me more about head flow than weeks of experimenting on my own or any book. I did a scrap Pinto head for days trying everything I could think of on the flowbench. Took it over to show him how I was the dog's bo11ocks now. He flowed it, grumped a bit, took it into his porting room and beavered away for 10 minutes. Recut the seats to a different profile. Put it back on the bench and blew my figures into the effing weeds. I learned a lot about flow and even more about humility.
John has not yet retired but will be later this year. Over the last couple of years he has done all of my and the company I work for head work, every time I have been to his shed I try to ask as many questions as possible and take in as much in as possible, he has also shown me how to use the flow bench, it didn't go in first time I have to admit. He has seen and done it all, building engines for Williams, DFV's, running his own dyno and engine build company and now porting heads in his garden shed. The junk he gets given given by people claiming to have 'best flowing head in the world' is crazy. his work is by far the cleanest and best I have seen and probably will ever see. All backed up by flow bench testing and 57 years of experience. In fact most of it is so minimal it doesn't look worth the money to our customers.
We took some Jowett Javelin heads to him(long story), again, sold to customer as dogs part, welded chambers(not easy on cast iron), oversize small stem motor bike valves, raised and filled ports etc etc. He had a std head out flowing their work in half an hour with standard 1940's valves and port sizes, by 10% peak air flow having never seen the head before, and huge gains at low to mid valve lift.
227bhp said:
If we were racing flowbenches he would have done well.
Sadly we aren't and an increase in CFM doesn't always mean an increase in power.
Neither does honking out ports and throats in decent stock cylinder heads like the one in question here, which is where most 'porters' without a flow bench end up. Sadly we aren't and an increase in CFM doesn't always mean an increase in power.
A flowbench is a useful tool amongst an arsenal of other tools. The head development has to be holistic as the head does not work in isolation to the rest of the engine, intake,exhaust, fitment in car, fuelling, transmission, tyres etc etc. Development is both empirical and theoretical. The op needs to research the engine and head then move forward by approaching a specialist with experience in that head/engine and put his thoughts across then listen then move forward rather than 'know' what is 'wrong' with the head in the first place and what will 'mend' it. It may well start them off down the path of doing their own modding.
Having said all that about tuning, I still make my best moves forward after doing something that loses power and learning from it, there are countless blind alleys and I have travelled many of them!!!
Peter
Having said all that about tuning, I still make my best moves forward after doing something that loses power and learning from it, there are countless blind alleys and I have travelled many of them!!!
Peter
99hjhm said:
227bhp said:
If we were racing flowbenches he would have done well.
Sadly we aren't and an increase in CFM doesn't always mean an increase in power.
Neither does honking out ports and throats in decent stock cylinder heads like the one in question here, which is where most 'porters' without a flow bench end up. Sadly we aren't and an increase in CFM doesn't always mean an increase in power.
It's quite often where owners of flow benches end up too - chasing CFM figures and not BHP/lbs/ft per 1000 rpm, 1/4 mile times, lap times etc.
227bhp said:
Hogging.
It's quite often where owners of flow benches end up too - chasing CFM figures and not BHP/lbs/ft per 1000 rpm, 1/4 mile times, lap times etc.
Do you have a flowbench or any specific examples of back to back tests where more airflow did not equal more bhp or are you repeating what you may have heard elsewhere?It's quite often where owners of flow benches end up too - chasing CFM figures and not BHP/lbs/ft per 1000 rpm, 1/4 mile times, lap times etc.
I posted our experience with heads flow tested on a superflow bench and then dynoed on a superflow dyno same operator and our heads made much more power.
https://www.pistonheads.com/gassing/topic.asp?t=14...
I also came across this article after seeing Mike mentioning the cnc ls7 heads.
http://www.hotrod.com/articles/hrdp-1203-7-top-ls7...
Note the paragraph.....
We were also interested to note that, in general, the heads with the better flow numbers produced better power, as you’d expect. But the flow bench does not tell the whole story; looking at flow alone, you might not select the SDPC heads, yet they outpowered some of the heads with similar or slightly higher flow numbers. There’s still some magic in port and chamber shapes.
Peter
https://www.pistonheads.com/gassing/topic.asp?t=14...
I also came across this article after seeing Mike mentioning the cnc ls7 heads.
http://www.hotrod.com/articles/hrdp-1203-7-top-ls7...
Note the paragraph.....
We were also interested to note that, in general, the heads with the better flow numbers produced better power, as you’d expect. But the flow bench does not tell the whole story; looking at flow alone, you might not select the SDPC heads, yet they outpowered some of the heads with similar or slightly higher flow numbers. There’s still some magic in port and chamber shapes.
Peter
Mignon said:
227bhp said:
Hogging.
It's quite often where owners of flow benches end up too - chasing CFM figures and not BHP/lbs/ft per 1000 rpm, 1/4 mile times, lap times etc.
Do you have a flowbench or any specific examples of back to back tests where more airflow did not equal more bhp or are you repeating what you may have heard elsewhere?It's quite often where owners of flow benches end up too - chasing CFM figures and not BHP/lbs/ft per 1000 rpm, 1/4 mile times, lap times etc.
Mignon said:
227bhp said:
Hogging.
It's quite often where owners of flow benches end up too - chasing CFM figures and not BHP/lbs/ft per 1000 rpm, 1/4 mile times, lap times etc.
Do you have a flowbench or any specific examples of back to back tests where more airflow did not equal more bhp?It's quite often where owners of flow benches end up too - chasing CFM figures and not BHP/lbs/ft per 1000 rpm, 1/4 mile times, lap times etc.
A flow loss = power loss, but not necessarily vice versa, but it does depend on what you term as or where you want 'power'. If you want an extra 10bhp at 9000rpm then quite often increases in CFM will give you that, but it won't necessarily help you beat the competition for instance if you've lost torque at xx rpm.
delcbr said:
The part that confuses me is widening the port at the valve guide to slow down air so it can make the turn instead of ramming into the long side bend. How much is too much and how do you know if it's needed to be opened up.
You measure the airflow around the circumference of valve head.
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