Air filter cover and outlet restriction?..any mods out there
Discussion
Has anyone done anything with the air filter cover that sits in the nose of the latter Griffs?... Or more specifically the outlet ID?,…
Having taken my cover out the other night to fit the new filter, I noticed that the bore was a lot smaller than the OD?... This part is made of fibreglass and due to the process of laying it up, the wall thickness varied from about 4mm to about 10mm depending on where you measured it… Having spent some time with a slot drill and round file I took it out to an average of 68mm ID but in comparison with the 3” pipe (76mm ID) it still offers quite a restriction…
Must say it's a bit of a nonsense upgrading to 72mm Plenum and bigger bore MAF if the first thing in the system is 68mm or smaller… or does it?? Could it be there to speed up the air in the system?... smaller bore quicker flow??????
Did think of cutting it off and making a 3” metal part out of say 1.2mm Stainless.. then pop riveting this onto the side to open it up but could this be detrimental??
Any thoughts on this… or is 68mm more than adequate to support 72mm Plenum further up…
It may also be worth checking yours as I could not believe how restricted and off centre the hole was… I easily took 6mm off one side of the bore!!
Having taken my cover out the other night to fit the new filter, I noticed that the bore was a lot smaller than the OD?... This part is made of fibreglass and due to the process of laying it up, the wall thickness varied from about 4mm to about 10mm depending on where you measured it… Having spent some time with a slot drill and round file I took it out to an average of 68mm ID but in comparison with the 3” pipe (76mm ID) it still offers quite a restriction…
Must say it's a bit of a nonsense upgrading to 72mm Plenum and bigger bore MAF if the first thing in the system is 68mm or smaller… or does it?? Could it be there to speed up the air in the system?... smaller bore quicker flow??????
Did think of cutting it off and making a 3” metal part out of say 1.2mm Stainless.. then pop riveting this onto the side to open it up but could this be detrimental??
Any thoughts on this… or is 68mm more than adequate to support 72mm Plenum further up…
It may also be worth checking yours as I could not believe how restricted and off centre the hole was… I easily took 6mm off one side of the bore!!
Some V8's have a very small induction pipe going into the AFM. I'm guessing the Griffith was designed with a nose intake to ensure cold air. Does the air temp make THAT much difference ?
Has anyone RRoaded an engine with a stubby v long induction pipe to measure the actual difference ?
Has anyone RRoaded an engine with a stubby v long induction pipe to measure the actual difference ?
you can expect a power decrease of 1% for every 7 degree C that the air intake temperature rises, so it wouldn`t take long to loose 30bhp on a 300 bhp engine, not that there is a great deal you can to do stop it, just try and minimise it where possible.
also would you really know you`d lost that power unless you were on a dyno at the time?
also would you really know you`d lost that power unless you were on a dyno at the time?
Del 203 said:
Oooooo !!! So will it be easier to get in/out ? 
Here's hoping, getting in and out is a right pain in the a**e.Seems to me that the whole air-box/induction bits are a bit of an after-thought with bits nailed together, so I'd have thought that a re-write of the airbox, smooth piping (as much as possible around the rad pipes so you can close the bonnet) with some reflective heat shielding might make the engine breath easier and release a few extra ponies though I don't know how much.
As a footnote, I had an M5 before and one of the cheap (cheap for a BM anyway) was to modify the air intakes, part of which was to turn them to face forward and create a bit of RAM air system. Claimed increases was about 10BHP so similar figures in the Tiv would be a pleasant suprise.
Bruce... thats the baby... but looks like you've gone over 3" also?... will do this when I'm back.... sure it will make a big diff!!!
I too will have to cobble pipes together as I can;'t get the ACT unit to work around the rad top hose... so will have smooth bore to flexi and then back again... Not ideal I know but better than flexi all the way?? To be fair the flexi I'm taking out are the straight runs and it's pretty smooth this silicon stuff when straight anyway... wonder if it will make for any better flow??
I too will have to cobble pipes together as I can;'t get the ACT unit to work around the rad top hose... so will have smooth bore to flexi and then back again... Not ideal I know but better than flexi all the way?? To be fair the flexi I'm taking out are the straight runs and it's pretty smooth this silicon stuff when straight anyway... wonder if it will make for any better flow??
I have been pondering over this bit as well. The problem area as I see it seems to be the kink where the pipe comes over the rad, under the bonnet and then up to clear the manifold. The series of corners especially when squashed by the bonnet cannot help the air flow. Was trying to figure out if several smaller bore pipes with a total area larger that the single one would be better or not. I guess a potential problem would be where the pipes merge into one as it might introduce turbulence. Another useful mod would be to somehow fit the filter under the body plate rather than above it. Trying to get the box back over the filter properly is somewhat frustrating.
TVR Beaver said:
Bruce... thats the baby... but looks like you've gone over 3" also?... will do this when I'm back.... sure it will make a big diff!!!
I too will have to cobble pipes together as I can;'t get the ACT unit to work around the rad top hose... so will have smooth bore to flexi and then back again... Not ideal I know but better than flexi all the way?? To be fair the flexi I'm taking out are the straight runs and it's pretty smooth this silicon stuff when straight anyway... wonder if it will make for any better flow??
Yup, about 3" I/D. I rolled and welded some SS sheet which I then bonded into the box with some JB Weld (or similar). The box is rigid enough to not require an adhesive with flexible properties. The ACT silicone hose was a nice snug fit.I too will have to cobble pipes together as I can;'t get the ACT unit to work around the rad top hose... so will have smooth bore to flexi and then back again... Not ideal I know but better than flexi all the way?? To be fair the flexi I'm taking out are the straight runs and it's pretty smooth this silicon stuff when straight anyway... wonder if it will make for any better flow??
I think the I/D of the original outlet averaged about 63mm so not bril! Gaining another 13mm has gotta be an improvement if you're running a large bore AFM (or especially if none at all); dunno what the 3AM/5AM chokes things down to.
If you need any more shots then let me know and I'll snap some off as this airbox is no longer in the car.
Del 203 said:
2Munkys said:
I'm currently (when I have time) knocking up a two piece affair which takes a different route to the side exit.
Oooooo !!! So will it be easier to get in/out ? I was gonna start a fresh thread with regard what I had in mind some time ago but it would have lingered as I've had little time to progress things materially.
My gubbins:
It's a two piece affair which comprises an Airbox and a Snout:
The Airbox sits over the filter in the same manner as the OE item but exits from the back (and slightly offset to the left). I've tried to make as much use of the limited space up front as I can. Volumetrically it's larger but only for the purpose of smoothing out the air path and increasing radii.
The Snout (or 'exit duct' if you like) is attached to the back of the airbox with three screws (captive nuts in the airbox). The snout passes over the radiators which is why its been made detachable.
The mould for the snout is complete and I've taken my first gel-coated GFRP item from it. The airbox is still at the plug stage and needs working before I can make a mould from that.
Whether or not it will be of worthwhile benefit I can't say at this moment; my aim was to minimise the convoluted airpath. My only concerns with the idea would be (1) not obscuring the airflow through the radiator, especially at standstill when you're reliant on the fans and (2) minimising heat transference to a redirected air route.
At the moment I'm using my first incarnation made from sheet ally and running a 90mm hose to the ACT tripple Jenvy plenum with the hose forming one gentle radius rather than a series of dog-legs.
Did look at this sort of thing myself... but though space was too tight not to interfear with the rad (fans)... and not to get too much heat soak... would be good to see your final offering...
I'll do the 3" steel bit first.. but will then go on to find a better alternative in the long term... Cheers... John
I'll do the 3" steel bit first.. but will then go on to find a better alternative in the long term... Cheers... John
I've done a lot of dyno testing on the airbox over the years when we were pushing the hp figures on the 5 litre griffs.
The std airbox is pretty dire as is the std filter and even the aftermarket filters are on their limit for big hp engines, but also the routing of the pipework over the rad hoses is a major limiting factor that nothing on the market really addresses.
My version modified the airbox into two halves and had an exit pipe at each end. one pipe followed the std routing, but now only carried half the airflow so was no longer a restriction. The other pipe exited the airbox to the driver side, down the rad and across the back of the rad (insulated to avoid picking up heat) to join in a Y piece with the original tvr pipe.
We found this new arrangement supported 350hp quite easily with negligable losses compared to a completely straight pipe.
The std airbox is pretty dire as is the std filter and even the aftermarket filters are on their limit for big hp engines, but also the routing of the pipework over the rad hoses is a major limiting factor that nothing on the market really addresses.
My version modified the airbox into two halves and had an exit pipe at each end. one pipe followed the std routing, but now only carried half the airflow so was no longer a restriction. The other pipe exited the airbox to the driver side, down the rad and across the back of the rad (insulated to avoid picking up heat) to join in a Y piece with the original tvr pipe.
We found this new arrangement supported 350hp quite easily with negligable losses compared to a completely straight pipe.
Sorry for the late reply, been away.
This is what I did to prevent the front lip of the bonnet compressing the tubing and reducing the choke:
This is where some (including me) also found a reduction in choke (top of fan shroud and coolant hose):
My ally box:
In situ:
I'm using 90mm bore tubing here which is why I've subsequently fitted some rubber sleeve over it to allow the bonnet lip to run along as the bonnet closes. Once closed there is no contact; I'm sure I can get away with using smaller bore however, even for the 5.4.
Like Joo suggests, I also think another area, for review at least, is the filter panel itself; my own experiment showed that disconnecting the red tubing at the stainless sleeve released another 11 BHP and 12 lb ft. How much of that was down to the filter (K&N) or the doglegs I dunno; my thoughts are the filter was the biggest obstacle at this point: bigger would be better.
This is what I did to prevent the front lip of the bonnet compressing the tubing and reducing the choke:
This is where some (including me) also found a reduction in choke (top of fan shroud and coolant hose):
My ally box:
In situ:
I'm using 90mm bore tubing here which is why I've subsequently fitted some rubber sleeve over it to allow the bonnet lip to run along as the bonnet closes. Once closed there is no contact; I'm sure I can get away with using smaller bore however, even for the 5.4.
Like Joo suggests, I also think another area, for review at least, is the filter panel itself; my own experiment showed that disconnecting the red tubing at the stainless sleeve released another 11 BHP and 12 lb ft. How much of that was down to the filter (K&N) or the doglegs I dunno; my thoughts are the filter was the biggest obstacle at this point: bigger would be better.
Gassing Station | Griffith | Top of Page | What's New | My Stuff