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..
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.
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 ?
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?
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?
abf is 16v though!
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!
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
Did you measure tumble and swirl too, or just ultimate flow?
How big is your flow meter?
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.
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
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
Quote from: G40 AD on October 31, 2010, 12:24:10 PM
?
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
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
apparenlty etka syas they are little different in length,
Hope this doesn't cause any problems for me , man in a shed put them in I assume he knows what he's doing !!
hope what doesn't cause problems?
Quote from: dub-disaster on November 03, 2010, 07:20:09 PM
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
looks like my inet valves are non g40 got a picture here do have to say lovley work on the head though and reasonably priced nice bloke too man in the shed
(http://i673.photobucket.com/albums/vv92/antywill666/photo-23.jpg)
there's nothing "g40 specific" about inlet valves and every big valve head ever made for a g40 doesn't have sodium filled exhaust valves to my knowledge. At least all the ones using 31mm valves.
actually stock inlet valves on a 1.3 (gt etc) are part number 030109601D and '99.3'
inlet valves on a g40 py are 030109601B and are '101.4'
so definately a different part number.
the 99.3 and 101.4 i think are length in mm of the stems. I can measure when i get home as i have both. If g40 ones are longer then perhaps they would remain open longer perhaps.
Quote from: hayesey on November 04, 2010, 09:37:19 AM
there's nothing "g40 specific" about inlet valves and every big valve head ever made for a g40 doesn't have sodium filled exhaust valves to my knowledge. At least all the ones using 31mm valves.
How do they deal with the heat? Are they the same composition or different to standard Mk3 1.3L exhaust valves, albeit a different size obviously.
I don't see how the length makes a difference, the cam lobe profile determines duration and lift. Longer length will just mean the hydraulic tappets are more "compressed" as far as I can visualise.
wont a 1mm longer valve be like a 1mm longer cam lobe though?
no because the lift is the ratio between the base circle of the lobe and the highest point of the cam. If a 1mm longer shaft meant it was 1mm more open at full lift then it'd also be 1mm more open at "closed" (therefore not closed at all!). That's why you shim solid tappets or have hydraulic tappets, they take up the slack between the cam and the valve stem top.
i get you yeah. Unless the g40 cam would mean normal valves are slightly open? I don't know.
They are a different part though for some reason.
yeah there must be some reason, although it's possible that that size was just what was available from the manufacturer with sodium filled exhaust valve.
but the inlet isnt sodium filled, but is longer.... they could've just used all 3f ones.
If you can measure both sets of valves please Pete that'd be ace.
I wonder whether a G40 cam has a smaller base circle than a GT or AAV one? If it did for some reason, that might explain why the valves were different stem lengths to ensure the same tappets could be used across the range. Can't think why they'd have done that though!
Or maybe the base circle is the same, but it was done to keep the tappet more compressed on a G40?
Quote from: Andy on November 04, 2010, 06:45:53 PM
I wonder whether a G40 cam has a smaller base circle than a GT or AAV one?
Or maybe the base circle is the same, but it was done to keep the tappet more compressed on a G40?
I was thinking the same about the base circle. What be the advantage of a more compressed tappet, presuming it was intentional? Less float?
I've been thinking about this, if the base circles are different as chest says doesn't this just put more pressure on the tappets ? The only reason for different valve lengths would Be different size head castings I'm probably wrong but just the way I see it.
G40 valves are obsolete now anayway so standard polo ones will have to do for me anyway. Be intresting to find the difference, next time I'm passing vw Tps I'll pop in and ask the friendly blokes at the trade counter.
I got a standard cam on my desk I'll measure the base circle with a micrometer tomorrow of any ones got a gt cam maybe they could do the same ??
all 1.3s are yeah
Cheers Pete - I have my shell sorted now so will be in need of your super supercharger services as soon as my 6n sells!
Me and Saf (grungeisdead) will bob over for some of your Supecharger expertise when you are free!
I was always under the impression a 1.0l had the same head as a 1.3l??? I have the G40 head already so I think I will just get the inlet flow improved and polished... would it be neive to think that if your were running enough boost that the standard port size of a G40 would be a more suitable size over the 1.0l???
After 4 days of driving my new shell as a 1.0l on a 4speed i'm ready to get the G engine in ASAP... planned to wait till April but that just simply is not happening unless I get my main G finished v soon!
cheers Ad
Here are some of my findings on the superflow 110 at college.
I'd be interested to see how they compare with the numbers the OP has.
7mm stem, 74mm bore adaptor, 10"H2O
Standard AAV
Lift" Flow in CFM
0.05 12.7
0.1 27.54
0.15 39.2
0.2 46.6
0.25 55.07
0.3 58.25
0.35 61.42
0.4 62.48
Standard AAU
Lift" Flow in CFM
0.05 11.2
0.1 23.9
0.15 32
0.2 41
0.25 46.2
0.3 47.5
0.35 48.1
0.4 48.3
AAU with 36mm Valve (+2mm oversize)
Lift" Flow in CFM
0.05 13.5
0.1 29.2
0.15 37.4
0.2 47.5
0.25 51.9
0.3 52.8
0.35 54.6
0.4 55.2
AAU with some work done on the short side and bowl area.
Lift" Flow in CFM
0.05 13.5
0.1 30.4
0.15 42.8
0.2 54.3
0.25 59.5
0.3 60.6
0.35 63.5
0.4 63.9
Ported AAV
Lift" Flow in CFM
0.05 16.4
0.1 29
0.15 38
0.2 49.3
0.25 59.1
0.3 64.6
0.35 66.8
0.4 69
I managed to get 79.8 CFM (discharge coefficient of 0.90) out of this port by using plasticine to increase the radius on the short side. There isn't enough room to get a TIG torch in these ports, so welding the floor up isn't an option.
Maybe I could use a pencil torch, but I don't have one of those.
I was trying to recreate this shape in the AAU port.
With the 36mm valve in the AAU there is little flow around the back of the valve, as was clearly shown by using a flow wand.
Unfortunately I found that the casting around the back of the valve (on the long side) is thin and I was into the water jacket before I had the shape right.
Maybe I just have a thin casting, I don't know.
With a little port work the AAU flows better than the AAV at all the recorded lift points,
(http://i133.photobucket.com/albums/q66/varnish5000/untitled-10.jpg)
The velocity kicks ass as the port is that much smaller than the AAV.
If I could get the air to flow on all sides of the valve I know it'd be a really strong flowing head.
But the only option may be to fill the AAV with JB Weld or similar.