Flow Tests Of Gti6 Head

[Mandic 0]

Hi,

 

Has anyone flow tested Gti6 head? I've seen some tests and if they can tbe taken for granted, GTi6 outflows Mi16 head for quite a lot, 20cfm to be exact. Which I think is a nonsense but still wanna check someone else's results.

 

Cheers

 

Ziga

[petert 554]

Don't forget to compare apples with apples. ie make sure both tests are done at the same pressure, or at least ty and convert them.

[B1ack_Mi16 67]

Don't forget to compare apples with apples. ie make sure both tests are done at the same pressure, or at least ty and convert them.

 

Apparently the tests were done on the same flowbench by the same guy, 28" test pressure.

Gti6 head was like 1-3cfm something lower on the very low lifts.

 

And like 20cfm more at the higher lifts.

 

Have lost the values now, but gti6 one seemed quite some better.

 

No idea which will flow the most in modified form though.

[Mandic 0]

Here they are:

 

XU10J4RS XU9J4

 

lift cfm cfm

1.27 41 46

2.54 83 85

3.81 123 124

5.08 159 156

6.35 195 184

7.62 227 210

8.89 257 233

10.16 275 252

11.43 290

[petert 554]

Those numbers for the XU9J4 are certainly consistent with my data at 28".

[Mandic 0]

Yes, I know, as I checked the results You have posted in big valve thread. So if Mi16 are correct then this is a bit worrying, I mean ok, yes, progress must be seen, but can Gti6 head really be that good!?

 

Cheers

 

Ziga

[huckleberry 0]

I heard (true or maybe just a nice story?) that just like the 206 GTI180 engine the head of the GTI6 engine went to Mecacrome to get a better design. I guess that would mean a few skilled people have had a look at it.

 

I always wondered why Dave isn't very positive about the GTI6 engine. With this new info I'm even more curious.

 

Tim

[Mandic 0]

Jup, me to... when I saw the flow data that's exactly what I asked myslef

 

But then again, AFAIK it took 4 yrs for pug to develope Mi16 head, or at least the one in 205T16.

 

Well still we have to look at the flow through complete cam rotation, not only high lift numbers as mid lift is imo more important. But if we take Mi16 R/S ratio in consideration maybe low lift numbers are even more important as it has better pulling power at low lifts, where Gti6 head would benefit on higher R/S ratio engines. But how much this all effects power in reality is another question.

 

But having more flow on smaller valves gives better gas speed.

 

Well I better leave this topic to someone who really know his stuff

 

Cheers

 

Ziga

[Sandy 189]

I think the GTi6 head is a great off the shelf head, I don't think there any cause to slate it, if anything the inlet ports look a bit big, but there are plenty heads like that that work, just about all the modern Honda heads for example. It has a nice chamber, multi angle seats and nice exhaust ports. Flow and valve sizes are not consistent handles on the potential of a head, Colin Satchell's 1930cc Mi16 made 229bhp at 7000rpm (@ Emerald) on standard valves, which is 220psi at peak power, not many beat that for BMEP!

Edited January 15, 2007 by sandy309

[smckeown 1]

I think the GTi6 head is a great off the shelf head, I don't think there any cause to slate it, if anything the inlet ports look a bit big, but there are plenty heads like that that work, just about all the modern Honda heads for example. It has a nice chamber, multi angle seats and nice exhaust ports. Flow and valve sizes are not consistent handles on the potential of a head, Colin Satchell's 1930cc Mi16 made 229bhp at 7000rpm (@ Emerald) on standard valves, which is 220psi at peak power, not many beat that for BMEP!

 

bloody hell that's impressive!

[Sandy 189]

True, my flame suit is on, just in case.

[Mattsav 1]

I flowed the mi16 and the GTI-6 both on an 83mm bore the gti-6 is far better in the mid range.

 

Where the gti-6 starts to tail off the mi16 just keeps going but this is fairly pointless as the total area under the curve is much smaller.

 

I'll dig out the flow graphs tomorrow but its definatley an inprovement over the Mi16 and you can have much nicer cam profiles as well.

[Sandy 189]

I'm putting one on an Mi16 bottom end soon, which should give an interesting comparison.

[Mandic 0]

Any news Matt?

 

Cheers

 

Ziga

[Mattsav 1]

Here you go.

 

Both heads flow tested on the same 83mm Bore whereas the GTi-6 should really be on an 86mm bore.

 

Flow at 0.5" very similar but the midrange flow is in a different league.

 

Combined with the smaller chamber it should make a good upgrade for an Mi16.

Plus you can use the GTI-6 exhaust manifold

[Mandic 0]

Thanks,

 

This really is a big advantage.

 

I havent seen GTI-6 head, but what's the main difference, I mean, according to the fact that Mi16 keeps going, are Mi16 ports a bit too big for fast road car? Maybe they were designed mostly for high pressure turbo engines?

 

Cheers

 

Ziga

[PumaRacing 1]

It really isn't as simple as flowing two heads and then saying one type is better than another. I've got flow tests of literally dozens of CVH heads from the days when I was flow testing every single casting to find the best standard ones for the Fiesta XR2 Challenge. You couldn't port the heads so the route to the best engines was flow testing as many castings as you could get hold of. To the naked eye they all looked the same but I've seen standard heads that flowed as little as 137 cfm at 400 thou (peak valve lift) and others with as much as 153 cfm.

 

At 250 thou the range of standard heads was from 102 cfm to 121 cfm. (The only exception to that range was a fairly expensive ported 'race' head from Power Engineering that flowed 97 cfm at 250 thou and 136 cfm at 400 thou although when you looked at how they'd butchered the valve seats and port shapes the loss became self explanatory. How they had the nerve to charge for ported heads that flowed worse than any standard one I'd ever tested is a matter I never quite got to grips with.)

 

An average standard engine in Challenge spec put out 80 bhp at the wheels on our reference rollers. The best ever engine put out 95 at the wheels and all of that was due to extra head flow on a bog standard head. It won the series so easily it wasn't really in the same race as the other cars. That particular casting was so precious that the team owner wouldn't entrust it to a courier when it was rebuild time. He had someone drive it down to me personally from Cheshire each time in a padded box on the front seat of the car with the seatbelt round it in case the car crashed.

 

In one race the driver missed a gear, bent a valve and cracked the end off the valve guide. I was away so they had to take it to the local engine reconditioner to get it fixed in time for the next race. They explained how important the head was and how carefully it needed to be repaired so that nothing got changed from how I'd done it originally. He nodded. They went away. When they came back to collect it this guy had hammered out the broken guide and smacked the punch into the port putting a big dent into it and then hammered a non standard oversized valve guide back in, butchered the seat when he recut it and near as dammit scrapped the whole thing. The owner was almost in tears when I got back and he phoned me up to tell me. The head came back in its padded box on the front seat of the car. I very carefully drilled the alien guide back out as it was in too tight to remove by force, fitted a new OE one and tweaked the seats back to how they should have been cut. Fortunately it made the 95 bhp again when it went back on the rollers.

 

I digress, as is often my wont. Standard heads can differ in flow by as much as 20% depending on casting shapes and valve seat profiles. Castings change at the factory over the years and there's no such thing as an average standard head. If you're allowed to port them this all becomes redundant though as they should end up at the same flow with the same ideal port and seat shapes. On that basis the Mi16 head is always going to beat the Gti6 one because it has larger inlets and the space to fit even bigger ones such as my 36.5mm ones. What they flow as standard is irrelevant other than it might teach a novice something about the port shapes to aim for where one head beats another.

 

Maybe an average standard Gti6 head does have better midrange flow than an average standard Mi16 one. Maybe it doesn't. It doesn't make a scrap of difference to me because I wouldn't be leaving the port or seat shapes standard anyway.

 

What you think you've learned from flow tests of standard heads isn't what you've really learned. When you know how to modify them to optimise them despite how they started off life then you might actually have learned something.

[Mandic 0]

Cheers!

 

Well I agree with the above. It is true that Matt and that other guy from who I got those flow figures on the first page made tests with different heads and got more or less same results. But on the other hand it is also true that Mi16 seats dont have 3 angle seats.

 

Maybe good comparison would be making both heads similar (3-angle seats, valve seat edge removed, ...) and then see what's what. + I agree with the fact that can be fitted with bigger valves, which is major advantage. But at first glance it seems that GTI-6 head (again according to flow figures posted over here) is a good upgrade in standard form (no money spent for flow job)

 

Cheers

 

Ziga

Edited February 1, 2007 by Mandic

[Sandy 189]

Need to see results on engines I think.

[Mattsav 1]

In general I find the std Mi16 heads to be fairly similar in flow terms. The only real exception was Maxi's old head which flowed and extra 10cfm @ 0.5" of lift.

 

As a cheap upgrade its worth considering. As an engine swap its also looking good as fairly low milage engines can be found from xsara VTS's.

 

You'll be very lucky to find an Mi16 that doesn't need a rebuild these days.

[niklas 1]

As a cheap upgrade its worth considering.

 

I think this is what we really learnt from this thread!

For those of us that doesn't afford well done head jobs, it's can be a mod that's worth every penny..

But obviously for those who want the most power out of their engines and are willing to pay for it, the MI has more potential to start from.

[TB_205GTI 1]

I think this is what we really learnt from this thread!

For those of us that doesn't afford well done head jobs, it's can be a mod that's worth every penny..

But obviously for those who want the most power out of their engines and are willing to pay for it, the MI has more potential to start from.

 

 

I totally agree!

 

When I had my 205 GTI 1.6 I replaced the head with a XU10 because in bog std. form it flowed better than the XU5/9 head. We have discussed this before, and if I recall correctly DB said that he couldn't see any reason to use the XU10 as a well prepped XU9 had better flow.

 

This is surely true if you can afford the big bucks on headwork. I couldn't so I used the budget solution

[smckeown 1]

Puma's bound to push the mi16 with headwork as that's how he puts bread on the table

 

With regards to the XU10 head, he did indeed post some very good information when he worked on my head. And the good chap that he is didn't charge me a penny for all the time he spent on it. He's a nice guy sometimes

 

So the gti6 head looks very interesting indeed out of the box.

[Dazza 4]

Thats the progress in engineering for you sean .My 306 Rallye was a cracking car although she was a little lardy ..but fun..