Shops set up to flow test U20?

[timurf]

Hey Gang,

I am sure that the answer to this question is buried in the forum somewhere, but after an hour of looking I am burned out.

I'm looking for a shop that is set up to flow test the U20 head. I'm in the Northeast, but don't mind shipping to get it done.

[2mAn]

TEM Machine in Napa CA set one up for mine and Will's (SLOroadster)... I should have an "after" number on mine soon

Just for fun...heres what mine did all stock

[SLOroadster]

Hey Gang,

I am sure that the answer to this question is buried in the forum somewhere, but after an hour of looking I am burned out.

I'm looking for a shop that is set up to flow test the U20 head. I'm in the Northeast, but don't mind shipping to get it done.

Rich at TEM Performance here in Napa is one of the best cylinder head guys in the country. As Simon stated, he's got two U20 heads on his bench as I type. He is busy, but I'm sure he wouldn't turn a job away.

Will

[timurf]

Thanks guys!

Simon I had already put your stock flow numbers into my Dyno2K library - so now I know where they came from. Love this forum.

I'm going to wing it and have a go at porting a spare head; not planning to remove anything from the intake but will open up the exhaust ports 'a little.' Then the usual work in the bowl area around the valves.

[2mAn]

Thanks guys!

Simon I had already put your stock flow numbers into my Dyno2K library - so now I know where they came from. Love this forum.

I'm going to wing it and have a go at porting a spare head; not planning to remove anything from the intake but will open up the exhaust ports 'a little.' Then the usual work in the bowl area around the valves.

Glad to help and share the info!

I agree that the intake side is just fine, its all about increasing the exhaust side.

Side Note: I think the exhaust "issue" is one reason why the "oversized" 1 5/8" header works well... Im an engineering student dropout so I cant say why haha

[SLOroadster]

Thanks guys!

Simon I had already put your stock flow numbers into my Dyno2K library - so now I know where they came from. Love this forum.

I'm going to wing it and have a go at porting a spare head; not planning to remove anything from the intake but will open up the exhaust ports 'a little.' Then the usual work in the bowl area around the valves.

Glad to help and share the info!

I agree that the intake side is just fine, its all about increasing the exhaust side.

Side Note: I think the exhaust "issue" is one reason why the "oversized" 1 5/8" header works well... Im an engineering student dropout so I cant say why haha

The biggest reason the 1 5/8 header works is due to its really poor design. It needs to be that big in order for air to flow through that immediate 90 degree turn as it leaves the port. Fluids don't like to make 90 degree turns, and most of the off the shelf headers have a 90 straight out of the head. The small tube headers create back pressure there, the larger ones create less back pressure. True race headers have less of a turn on exit, allowing better flow out.

I still need to get over to TEM and see how those headers flowed.
Will

[Daryl Smith]

"....its all about increasing the exhaust side."

....Increasing the FLOW, not the size of the port. I am not familiar with the U20 head, but, typically, (as with the R16 head) the portion of the port past the valve is oversized and the choke point is likely around the valve guide and short side turn. ymmv

[timurf]

Hopefully it is just a matter of time before someone does a CFD analysis of the stock heads in a program like FloEFD. But getting an accurate model would be a daunting task, probably requiring sectioning a head and 3d scanning the stock ports and combustion chambers etc.

But imagine the fun you could have messing around with seat angles, port radii, and unshrouding the valves, helping to remove much of the speculation and save time-consuming experimentation. After all, this is how the OEMs design heads.

Of course this would not be the final word in HP, but it would sure get us a whole lot closer.

[timurf]

[/quote]

The biggest reason the 1 5/8 header works is due to its really poor design. It needs to be that big in order for air to flow through that immediate 90 degree turn as it leaves the port. Fluids don't like to make 90 degree turns, and most of the off the shelf headers have a 90 straight out of the head. The small tube headers create back pressure there, the larger ones create less back pressure. True race headers have less of a turn on exit, allowing better flow out.

I still need to get over to TEM and see how those headers flowed.
Will
[/quote]

Yes, I am sure other owners of these common headers (like me) notice the darkening of the ceramic coating at the 90 degree bend at the bottom. That's a good indicator of gridlocked exhaust gases.

[Gregs672000]

I'm really looking forward to the results of the header testing. I've been contemplating a different header for some time now, but I would like some data that shows this is truly a big issue. I'm not sure what size piping I have... what should the outside circumstance be to determine internal size?

Also, will this testing relate directly to performance?

[JT68]

Flow testing headers is a complete waste of time, money and effort- it simply doesn't equate to power gain. Anyone who tells you otherwise is just taking your money.

Watch the youtube videos of engine dynos & restricting the primary tubes on headers. As in those videos, the header primary tube is not the limiting factor for the U20 engine. Flow testing would never show that. An engine dyno is the only real world method.

So far, the only 1 5/8 headers I've seen that make ANY sense at all are those coming out of Australia.

[Gregs672000]

Flow testing headers is a complete waste of time, money and effort- it simply doesn't equate to power gain. Anyone who tells you otherwise is just taking your money.

Watch the youtube videos of engine dynos & restricting the primary tubes on headers. As in those videos, the header primary tube is not the limiting factor for the U20 engine. Flow testing would never show that. An engine dyno is the only real world method.

So far, the only 1 5/8 headers I've seen that make ANY sense at all are those coming out of Australia.

I was wondering about that, and thus my post above. What is it about the Aussy header that "makes sense" vs others? Tube Length? Diameter? Bends? We know Lou has developed his on a dyno, but i wonder how the different options compare. If someone's making 214hp it can't be TOO restrictive I wouldn't think, but a torque curve would tell us a lot more. Thanks!

[JT68]

IF someone is making 214 HP NA on an actual calibrated engine dyno (not a chassis dyno), it isn't because of that header-that suggestion is pretty funny. I'd say it has a lot more to do with the engine build despite the header. The little stubby collector used on most headers is tuned for like 10k RPM, so no it isn't restrictive, but it isn't contributing anything at all.

Regarding flow testing pipes it's pretty obvious, if you hook up a giant vacuum cleaner to a 1/1/2" pipe vs.1 5/8" pipe, the 1 5/8" will flow more-all day long- High school level math will tell you that. So why pay a bunch of money to confirm that?

Fact is a single U20 exhaust port isn't outflowing a 1.5" open pipe, so what is the point? Nope sorry to burst that bubble.

The real point is for the vast majority of U20 street engines, the header is not the limiting factor, so increasing to 1.625 makes no sense-that is why most headers for U20 sold in the last 30 years were 1.5", not because someone could not make a 1.625 header. Higher primary velocity with the 1.5 inch is probably better for driveability in most street cars in reality.

If you are running balls-wide-open all the time, yes, the AU header clearly is far better optimized for HP and torque in the upper RPM range- anyone who has some experience with header design can see that. Since the development work was done with an a engine dyno to optimize torque across the power band, that is a huge difference over "regular" headers. Better tube length, better bend layout, better collector design- better everything, no question.

Credit where credit is due - I have no vested interest in the AU headers - they are just very well thought out.

[Gregs672000]

Appreciate the info and experience JT. At this point I'm probably not going to worry too much about it for today... I always need SOMETHING to do to the car, so maybe a different header is further down the road...

[JT68]

Right, for most U20 rebuilds there will be little if any gain from switching to a header (except possibly the AU header), the factory manifold was very efficient. Taking the Tri-mil design and changing to 1 5/8" primaries is not very useful-just marketing nonsense. Kinda like running 2" primaries on a 350-wishful thinking.