Throttle bodies air filter vs trumpet length - Saxperience

Pugdjw · 22nd July 2016, 23:53

What would people recommend when it comes to bodies. Slightly shorter trumpets with a full size itg filter or longer trumpets with a slim itg filter. Will the slim filter be restrictive ? Or is it better to run the longest inlet as possible with a slim/no filter.

welshpug · 23rd July 2016, 09:21

what do you mean by slim filter?

Pugdjw · 23rd July 2016, 12:45

The depth of the filter. I've got the itg jc filters in 25mm ( slim) and 40mm (standard )

welshpug · 23rd July 2016, 13:58

youll need a deeper filter if you fit longer trumpets, you meed a minimum clearance from the trumpet to filter.

Chipwizards · 23rd July 2016, 22:21

I think he means should he fit longer trumpets for the resonant length improvement with a slim filter, or shorter trumpets with a deeper filter.

Pugdjw · 23rd July 2016, 23:32

Quote:

Originally Posted by Chipwizards

I think he means should he fit longer trumpets for the resonant length improvement with a slim filter, or shorter trumpets with a deeper filter.

That's what I meant mate. I was wondering if I could increase the length of the trumpets and reduce the depth of the filter and if it would make any difference. But like welsh pug said I suspected their would be a minimum surface area needed between the filter and the end of the trumpet.

I was always just under the impression the longer the overall inlet tract the more power etc they created.

KamRacing · 24th July 2016, 10:03

You will make better power with longer trumpets but you are limited by the packaging. You could run a smaller width filter by welding the backing plate further up the trumpets.
What setup do you have?

Pugdjw · 24th July 2016, 10:49

Quote:

Originally Posted by KamRacing

You will make better power with longer trumpets but you are limited by the packaging. You could run a smaller width filter by welding the backing plate further up the trumpets.
What setup do you have?

I'm running the satchell/sandy brown 16v gsxr 1000 bodies , there is very limited room in the s1 rallye engine bay. The base plate is attached to the back if the trumpets. It made 162.9 bhp when it was mapped I just wondered if there was any gain to be had by increasing the length by say 30-40mm.

Chipwizards · 24th July 2016, 18:27

Fit a radiator without a header tank and fit a separate header tank. Modify or remake the engine mounts to lean the engine forwards and create more space behind it. Fit long trumpets inside the biggest airbox you can fit in the space you have and draw air from a cold source via a boxed air filter assembly.

The oil returns to the sump are at the front of the head so oil drainage isn't compromised by leaning the engine forwards.

The M3 has such a setup (albeit RWD but it is configured this way for exactly the same reasons. In the motorsport versions air is drawn through a panel filter beside the radiator so it gets cold, filtered air.

Look about 2/3rds down, you'll see what I mean.

axsaxoman · 25th July 2016, 10:06

you need to read a bit to understand what will be best for your engine .
rpm range where you want the best compromise etc
a book by A graham bell
"four stroke performance tuning" haynes book ISBN 0-85429-275-6

--not expensive and will tell you all you ever need to know. lots of other books but most are very geekie and very deep into fluid dynamics
simple answer is you want distance from filter to be be same as dia of trumpet --which is hard to do --so a plenim chamber with remote filter is another option--dia of tubing from filter to plenim is also important
or just cut the bulkhead and get more space

I would add that you ain,t going to suddenly gain a huge bhp gain --without also matching exhaust manifold +system just as precisely

BUMMERS · 25th July 2016, 14:42

^are you on commission for that book?

axsaxoman · 25th July 2016, 14:53

no . lol
i can suggest others --but that one is about as simple as it gets and really geekie fluid dynamics books cost mega money

welshpug · 26th July 2016, 05:03

You'll most likely have a good ballpark total tract length already if its a satchell inlet, do you have a cut scuttle?

Pugdjw · 26th July 2016, 12:25

Total inlet tract is about 260-270mm standard iirc. Ye the scuttle is already cut to allow air to get to the filter. I just wondered if there was anymore readily avalible power by increasing the trumpet length, but as chipwizards already mentioned it would involve tilting the engine forward slightly to create more room for the trumpets to me extended and to be able to accomadate the filter.

Chipwizards · 26th July 2016, 22:33

Tract length is totally rpm specific.

axsaxoman · 27th July 2016, 08:27

Quote:

Originally Posted by Chipwizards

Tract length is totally rpm specific.

As in you specify where you want max bhp or torque and make inlet length+ dia to suit using correct formula + same for ex manifold choose type primary lengths and where the first box is .
So to get all correct you must start with cam profile which will decide where max bhp +torque occur .
this is why I suggested you do some reading and you will then see the complexities and choices/compromises you need to make to get best for your engine spec+uasage

it is for that reason I made downdraft manifolds for 8 valve engine + 90degree carbon trumpets for the 16v engines--to get ideal length --t bodies don,t car which way up they are

Chipwizards · 28th July 2016, 00:11

I don't suppose you've ever seen the trumpets fitted to the 20v version of the Toyota 4AGE engine have you John? They look awful, where the body ends and the trumpet bolts to them they go through a tight 90 bend and 'wiggle' between the fixing bolts before coming to the bellmouth.

I had a kit car in with one of those engines and I spent an age making some nicely radiused trumpets of suitable length (because there was room to do so in the new chassis) and I was expecting to see a healthy gain, given how grim the stock setup looked. Anyway; nothing. Not a sausage. Exactly the same power and torque for my day's efforts. Lesson learned, just 'cause it looks bad don't mean it is. Ergo, just cause it looks good.... :-/

axsaxoman · 28th July 2016, 08:23

yes we all had learning things like that one --could be the bend caused swirl which speeded up the air like a tornado and mixed fuel well--flow bench is the only way to know for sure --but even that don,t tell you how well the fuel is mixed or how it will act in combustion chamber
I found on 8v vauxhall heads that actually building a hump at bottom of port to make the inner bend smoother+ longer distance to go round the corner of port -made it flow better ,even though it made port smaller on the bend --go figure
i even made an 8v valve ax head totally downdraft by welding in new inlet ports at 45 degrees to head face --could see all the inlet valve like the ford MAE engines of old --difference was certainly very small and not worth the days spent doing it--but it do look the dogs bollocks.
i remember "car+car conversions " doing a test on inlet manifold lengths on the cross flow --ideal length would have meant the webbers would be sticking out into the inner wing on a mk2 escort it was that long