Jenvey DTH Throttle Bodies

Hi guys, bit of a specific technical question regarding the above. Does anyone know how much these flow in CFM at 10'' or even at 28''?? The TMW setup I have is giving me a bolt on loos that I am not entirely happy with. Any results would be greatly appreciated. Thanks.

 

I have these in 45mm size and they flow loads of air - enough for 240-odd hp anyhow - dont have flow figs I'm afraid

Suspect they are restrictive to hp (think it was additional 16hp in tests with DCOE-type 48's) but keep the midrange up

Why did you get TWM ones ?

 

Err, through Bildon motorsport, err, exchange rate was good, err, integrated fuel rail & FPR & trumpets, err dunno really, itchy trigger finger on the net I suppose!! To be honest the TMW's flow 151 cfm which is more than he head, however, actually on the head I loose about 10cfm. I was interested to find out if anyone had any numbers for the Jenveys, or if not, does anyone have a set they are not using that I can get tested? Bolt on losses are just not acceptable in my book!!

 

thats crap - send em back......angle of attachment too shallow ? the Badger-5 / jenvey dth's are a superb almost downdraft design IMO

Bill will have some but I doubt he'll lend you some now you have gone to the darkside.....my car wont be moving from mid sept till spring so could take mine off and have em tested - where you at ? dont fancy posting them....

very thorough job you are doing flow testing with these bud ! nice one. I have not forgot about our pm, been dead busy with work / kids

 

Let me check with Jenvey on test results they have.
Originally they were designed to be 48mm bore, but in the main this was too much for most applications (but remains an ordering option)

 

.....and on the list of to-do items to check out

a decent ported 16V head (on stock valve sizes) should do 145-150 CFM at 10" on max valve lift so the flow sounds quite well matched - so the angle of attack must be wrong, theres a weird section change, or there's gasket in the way.....

 

I'm just outside Reading. How about you? All in all, the fit and angle looks pretty good i.e, no change in angle from the head. The one item that could have an effect is, as Bill says regarding the Jenveys, these were likely to have been designed for a larger throttle plate as there is an internal "step" where the unit transitions from the throttle to the manifold so to speak (the mani is slightly larger to the tune of 2.5mm all around - leading me to believe these were initially designed to be 50's) All very strange though.

Bill, if you can get some results from Jenvey that would be fantastic.

Rob, 145 - 150cfm from a 32mm inlet valve is a lot (25% up from std 120cfm), that must be some porting job, my BVH is around that point, I say around because it is not quite finalised...

Does anyone know how to load pictures on here? Pictures speak a thousand words I find!!

 

You need to upload your pics to photobucket.com or another photo hosting site (it's free) and then post links to them.

Could the internal step be ground out? I guess pics would help

 

mani?
these TWM's not direct to head? unlike DTH Jenveys I do.

 

Im just south of Manchester - not exactly near unfortunately......

The B5 dth bodies are angled more upwards compared to a traditional dcoe-type design - very nice - get a downflow effect to the valve. Sounds like yours are level cf. a dcoe setup (carbs have to sit level as they have a float chamber - tbs can be at any angle...)

Sounds like you have separate body and manifold - and that they dont match which is poor - the whole system needs to be seamless all the way to the valve - as Mike suggested these can be ground to match but the idea is that the sectin does not change to the valve or ideally gradually tapers smaller all the way to increase gas speed - not smaller, then bigger...

Thats a reasonably good porting job yes - not a patch on mine though

 

Unfortunately my pictures are on my work machine, so I wil try to get these uploaded tomorrow evening when I get back home for you to take a look at.

The TMW's are DTH and have some downdraft angle, the same angle as the ports in the head so in theory they should flow well on the head. The bodies fits well on the head, with no steps, so again, there should be no real loss from this either. Very strange.

Regarding grinding out the step, it should be possible to reach this, however, I had thought about this and although it is probably causing a level of turbulence, I am looking for somewhere around 20 cfm extra from the bodies in order to get no loss when on head and I don't think removing this will yield that much, hence the question!!

Mike, how much are shed heads? I would quite like to get one on a flowbench for comparison purposes, a CFM number means nothing without a yardstick to compare against...and on the subject of comparison, Rob, do you have any CFM numbers for your full spec head?

 

Im confused now - so wheres the step you originally mentioned ? (post 7)

 

About a c.m past the throttle plate from memory.

 

that dont sound right to me.....(the body not your info).......it should be smooth all the way through IMO

sounds like they have one casting with option of several butterfly sizes

 

Yep, thats exactly my thoughts on it. They taper nicely into a 50mm x 35mm shape at entry, not that it is helping!!

 

Visit www.photobucket.com, register an account, load your photos into there and paste a link into here. Post the link commencing with into your threads.

Easy-as

 

are these them ? with vertical butterfly spindals

http://www.twminduction.com/ThrottleBody/16_valve_vw.html

They look the biz - some real pics would be nice to see. Says they are available with 45, 48, and 50mm throttles which explains the step - well shoddy that they have just left a step though, that is going to slow gas speed down a load and potentially create turbulance

massive difference in cross section between 45's and 50's and presumably the runners have been sized for 50's.....1590mm2 vs 1963mm2, difference in section of 19%, thats A LOT in gas flow

like I said above, they need to be the same cross section all the way or gradually taper smaller, not the reverse

 

Re. head flows, these boys are pretty good I reckon, in Manchester

http://www.cncheads.co.uk/products.html

16V on stock valve sizes tested as a bare head, i.e no filters attached, max lift (500 thou)
(in) 117-142 (inc. 21%)......std fig agrees well with your measured 120cfm
(ex) 91-104 (inc. 14%)

(flowed Vuax XE head does 160/140......capable of 245hp at 8K so that tells you what kind of flow is required for what power - stock valves are big though with an 86mm bore - new Duratec will do 180/140.....another league, on stock valves also, good for 280hp at 8.3K)

8V on stock valve sizes
(in) 81-106
(ex) 61-77

Big Valve 8V
(in) 81-118
(ex) 61-80
(note that even a flowed BV 8V head only flows as much air as a stock 16V head does....and a modded BV pinto will flow 130/85, good for about 200/210hp so figures of race vw 8v's doing 180-190 are probably about right)

20V std valve sizes
(in) 150-152
(ex) 110-150
(note a 20V does not flow much more into the engine than a modded 16V head which backs up power figs for works versions of these engines and 'heresay'. Also, this head is good for 500hp apparently)

The BRM data I have for 16V on stock valves says
(in) 87-106 (inc 22%)
(ex) 66-92 (inc 39%)
these heads had ports done and used stock valve sizes but the valves were 'modified'. The flow figs are not the same (presume measured at different valve lift) but the inlet increase of 22% is very close to that seen with CNC heads. Not sure whats going on with the exhaust flows - 14% CNC vs 39% with BRM.......maybe BRM really were the mutts nuts.....headwork was gone by an "ex-F1" engine specialist apparently

also at 10" WG

 

what are the throttle plate angles on the TWM?
On mine/jenvey they are horizontal throttle plate which do not open 90 degrees, to the butterflyintroduces some tumble into the port.

Sounds like your large step is the culprit from the land of "bigger is better"

Worse still from how you describe the step its likely in line with your injector also, so a high speed to low speed flow area which wont be helping flow to carry fuel into the combustion chambers.

 

they flow good numbers though.......polishing does very little, its the shape that counts !

Years ago I bought a head from Autosprint in birmingham for an MGB - looked the mutts nutts - fantastic finish to it, polished to see your face in it

Fitted it all up and went to Aldon for a RR setup....result.....1hp gain

Friggin furious but tought a good lesson


EDIT: this makes no sense anymore as Hotgolf removed his post slagging off the CNC heads port finishing quality - cheers Mart !