BVH flow bench findings...

[jez1272gt]

Spent all day having my standard cylinder head and my ported and polished, big valve cylinder head flow benched today, interesting finds discovered and the fact that 'less is more' was really high-lighted(if you know what you are doing). I will only give an overview as this is part of my final year dissertation, however, once i have submitted it at the end of april i will put up the full data (permission dependable) and full conclusion and evaluation if anyone is interested!

For now though... Think again before putting big exhuast valves in your cyclinder head, with the correct port work you will see the same if not a better flow rate using the standard valves (this will bring down EGT's allowing your timing to be advanced). Do not enlarge the original inlet port diameter as it is oversized for optimum flow to begin with..

I was pleased with the results of today and my ported and polished big valve head is flowing approximately 30-35% more air (across the lift range) than the standard head, however the main man is certain there are improvements to be had across the board from taking a different approach to the way the traditional G40 head work has been done..

[Tommo]

Yeah. If you find a bloke called optima21 he made his own flow bench and did his own head.


Its no secret that the inlet ports are too big though, IIRC for optimum performance they need opening up above the valve where all the restriction is and then the port size reducing and shaping with belzona. Its all to do with getting the fluid round that viscious 90 degree bend above the valve.

I would love to make my own flowbench (out of old vacuum cleaners of course!) and gas flow a head but I just never have the time.

It would be interesting to flow standard heads with 7mm and 8mm valve stems.

[dub-disaster]

Very intresting to know this, makes me wonder about my bvh   although I would hope that this. Flowed better than just a polished a parted head as it was probably double the price !! What size valves are you using In yours jez the usual 2mm bigger? Mine seem to be 33m wit h I think is slightly to large am I right ?

[hayesey]

interesting, will look forward to hopefully seeing the facts & figures.  What did you compare then?  A standard head, a ported head with standard valves and then a ported head with larger exhaust valves?  Who had done the porting out of interest?

[giorgio]

From a discussion with Dom years ago he reckons that a 1.0 head is best to begin porting as there is so much material to play with.


On a similar Golf related note. - JP of JNL Race can get better figures for a standard ported head than G-Werks can get from a ported BVH. Think this was a ABF head.

Which uni are you at?

[PeteG40]

abf is 16v though!

[jez1272gt]

Im at Surrey doing Motorsport Engineering.

Im not saying there are any secrets in the findings, just that i shall put it up for those who dont know/may find it interesting. Im sure this has been done before by someone however i have not found any information like this since perusing the Polo/G40 forums for the last 3-4years.

We used two cylinder heads, a standard one and my ported and polished, big valve head. The BVH is a big of a mixture, I bought the head from Pete a while back, it already had the big valves and some very light porting and polishing, i then took it to Paul at Race Power Motorsport who did some port shaping and paid attension to the valve area and short side radius etc etc..

The conclusion from yesterday was that the head is very good and should be comfortable for over 200bhp for those intersted in figures, but the inlet air speed was a little slow meaning throttle response will lack a little and the outlet speeds were a bit high causing high exhaust gas temps. With a fresh head these could be overcome and possibly even more flow acheived...hmm!!

I'll stick the results up as soon as possible for people to check out!

[polo classic]

What valve sizes did you try? Did you try "UK spec bvh", eg only larger exhaust valve 31mm or the other 37/32 and 38/33 mm combo's


http://www.gofastnews.com/forum.php?s=5055cedc986980b46587f5ecd7db4a81

[Yoof]

Did you measure tumble and swirl too, or just ultimate flow?

How big is your flow meter?

[jez1272gt]

sorry for slow reply, had loads of uni work to complete recently. As bad as it sounds im not sure exactly what size valves are in but im fairly confident that they are the usual 2mm oversized exhaust with standard inlet. I'll check  We only benched these two heads/valve combos as i was paying for the time and money is not something i have a huge amount of at the moment lol. I would love to try some other combos and will probably look into getting another, more optimum head speced up in the future just for peace of mind and to try and bring down the egt's for a safer engine!

I have already layed down the gauntlet for the head man to make a better al-round cylinder head without going oversized valaves and hes confident he can achieve this so it will be interesting to see what the outcome is if i can afford to have it done in future.

Yoof, we only measure the ultimate flow and the air speeds at differing points of the ports, ie, the mouth, throat, and neck, in both the wall and central positions. I assume the bench is fairly large as it will flow 700-800bhp rated heads and possibly beyond i would imagine.

[G40 AD]

this topic looks really interesting were there any more findingd on this? interestingly last time i had a G engine down at my usual engineers he was saying something very similar in a sense that the size wasnt bad it was more the angle and that just working away the metal in that caorner would make a vast difference.. I have just picked up another G engine and I am thinking of having this work done...

I was always told that it was a bit of a dark art p&p'ing the G40 heads and getting them right... is there any advice/pointers i should be giving my engineer or infact anyone that is very specialist on G engines?
Also is there anyway to confirm that the valvea are sodium filled? just want to be certain before i spend money on the head not that i have any reason to doubt this but wouldnt want to spend all that money to melt the head!

Cheers,

Ad

[shaun_89]

I agree with the 1.0 head being the best starting point. The 1.3 ports are too large to take out to a much better shape.
Interestingly i put a standard 1.0l head and spi intake on an aav and although i havnt got round to having it rr'd its definatly faster even with the smaller valves. It feels stangled at top revs but then again so does a standrad aav due to the way its been engineered for power/torque

[PeteG40]

?
Also is there anyway to confirm that the valvea are sodium filled?
Cheers,

Ad

g40 valves have a circular indent in the flat of the valve (inlet and exhaust)  1.3 and 1l ones don't

[dub-disaster]

Any difference in inlet valves between g40 and non g40 other thanthe little indent think my inlets are non g40 as they have no indent on them

[PeteG40]

apparenlty etka syas they are little different in length,