Throttle body sizing - the theory behind the flow, YO

[superkarl]

so this comment got me thinking:
VWVortex.com - FrankenTurbo F23 Project: FrankenTT is go!

now Issam is quite a respected fella in the vag tuning world, esp 1.8t, and is responsible for the following thread:
VWVortex.com - TECH : TEST 1 OF 3 | Throttle Body Sizing
which although quite an old test, still has some credibility.

so what am i getting at.

Well MOST people on here and all over the tuning world run 63mm or 2.5 inch pipe work for their boost hoses.
and there is lots of ummmming and arrrring about inlet manifolds and throttle bodies and the benefits that can be had.
If you havnt already read tufftys thread, he and bill recorded some considerable gains through a large plenum/runners alone, promising for alot of people pushing respectable power.

so what about the Throttle body. Well apart from Issams tests over in the US quite some years ago there is much more speculation to the benefits of a larger one. After tufftys recent update it seems he will be doing some testing on a larger one soon-ish, although i dont knwo what tb it is and the sizing. hopefully he can share.

so my thoughts on this,
63mm boost piping, as used by myself, has a wall thickness between 0.5-1mm, lets say 0.5mm for now, 1mm seems thick to me.
The pipe has 62mm internal diameter, and an area of 3019mm^2.

so now lets take our standard 60mm ID throttle body as found on our S3.
Area of 2827mm^2. Already some way off the boost pipe size.
Now if we apply Issams theory of 80% useable area in the throttle body (due to the butterfly and the pin on which it rotates), we have a useable area of 2261mm^2.

2261 Vs 3019

quite a difference im sure you'l agree.

now as we all know and have come to learn, 'its all about the flow' TM

so if we are going to have the 'ideal' setup in our boost/inlet system, we need a throttle body, that at 80% of its internal area, matches the area of our boost pipes. Afterall, we are moving a HUGE volume of air.

So if we spec a 70mm Throttle body, which has a 3848mm^2 internal area, and 3078mm^2 80% useable area, we have a much better match.
3078 Vs 3019

so in theory, a 70mm throttle body, based on Issams 80% comment, would be ideal.
Now if we refer back to his tests in the above thread, 70mm seems the best option to me. Backing all this crap up? I think so.

If however Issams 80% is a little high, and tbh im thinking it might be. And we apply a 90% (10% restriction from butterfly assembly) Then a 65mm TB might cut it.
65mm has 3318mm^2 area. 90% = 2986mm^2

2986 Vs 3019. A tad better.

i started thinking about this for my own build, and the fact il hopefully be using a large plenum/runner inlet. And i want a TB that will 'match' the flow of my pipe setup. Then Issams comment on vortex got me thinking basically.

so this is some food for thought when you are spec'ing your build, and whilst the standard TB will work, and will be fine, we all want cheap gains, and a TB isnt all that expensive, and on big turbo builds, may yield some worthwhile horsepower.

Next step, find a suitable Tb.

EDIT:
list of TB and internal diameters
standard = 60mm
2.7TT S4 = 65mm???
VR6 = 65mm
NA S4 = 70mm
R32 = 75mm
RS4 = 75mm
Hemi = 80mm

the above may be edited. subject to measurement

 

[Dani_B19]

V6 one like im running off a golf 4 motion.

 

[superkarl]

65mm ID?

if we say the tubing is 1mm thick, 61mm ID, area of 2922mm^2
65mm TB = 2986 @ 90%
and = 2654 @ 80%


so its good if the area of butterfly is 10%. still gains to be had if its more. Which shows in the testing by Issam/Unitronic

 

[JonBoi25]

I like it ! Something I hadn't given much thought with this car, I looked into in on previous cars but they were N/A. I thought it would be pretty tricky upgrading the TB with a standard plenum (inlet manifold) Have you got an uprated one ( sem or something ? ). Thanks , Jon

 

[superkarl]

I like it ! Something I hadn't given much thought with this car, I looked into in on previous cars but they were N/A. I thought it would be pretty tricky upgrading the TB with a standard plenum (inlet manifold) Have you got an uprated one ( sem or something ? ). Thanks , Jon

you either need a TB adapter plate, changing the bolt pattern.
or in my case, custom inlet, il have it drilled for whatever bolt pattern the TB is.

 

[badger5]

simple test would be check pressure drop across the throttle vs airflow thru it... and losse's across the setup can be quantified

the part throttle suggestion are dependant on the ecu opening of the throttle, which is not 1:1 for the record and managed by Me7 and subject to tuners influences.. (mapper etc)

wot vs wot is a fair comparison for peak numbers.

throttle never opens 90' more like 82'

 

[<tuffty/>]

Wait no longer

The TB I am going to test is from an S4... fairly sure its an NA S4 or maybe the super charged one... not actually sure as I was just given the TB to try..

I am with you on the sizing though... 70mm seems to be a sensible step up to maintain cross sectional area... people use the R32 TB purely due to availability... most of the info on 70m TB's seems very vague and INA while they have been supplying them for a while always seem to grind the part numbers off...

S4 throttle body... be aware this will need a bead welding on much like the R32 TB else the hoses will pop off...

Part numbers...

The one that INA have supplied more recently is from a Porsche I believe...

This has a non symmetric pitch on the fixing bolts and the electrics protrude back which may requiring clearencing of the adaptor plate of manifold depending on how its being fitted... the one I saw also had a non VAG connector so was supplied with an adaptor...

On the subject of wiring, I had to extend the TB wiring due to the size of my inlet etc... the R32 TB was a little stretched also from memory when I fitted this to my std inlet...

<tuffty/>

 

[superkarl]

simple test would be check pressure drop across the throttle vs airflow thru it... and losse's across the setup can be quantified

the part throttle suggestion are dependant on the ecu opening of the throttle, which is not 1:1 for the record and managed by Me7 and subject to tuners influences.. (mapper etc)

wot vs wot is a fair comparison for peak numbers.

throttle never opens 90' more like 82'

peak being what sells such modifications.

not a simple test to perform at home DIY.
Im basing this mod on theory alone. Its enough to convince me to upgrade to a larger one anyway.
me having 63mm boost pipe, a GTX2867 pumping air but a measely 60mm throttle body.

whether it yields results, well, hopefully you and tuffty can tell us in due time. Issams results tend to get questioned and discredited quite often, with it being quite old.

 

[<tuffty/>]

The S4 one I have is 70mm, R32 is 75mm

<tuffty/>

 

[superkarl]

is that internal diameter?
ive found conflicting sizes and dont want to get ID and OD confused.
for instance in issams tests the 2.7 S4 one is 65mm ID.

 

[Dani_B19]

Ill check the internal diamtere friday karl, im sure its 70mm or there abouts OD wise.

 

[superkarl]

its the Internal diameter thats important. 70mm being ideal

 

[<tuffty/>]

is that internal diameter?
ive found conflicting sizes and dont want to get ID and OD confused.
for instance in issams tests the 2.7 S4 one is 65mm ID.

I can measure it again at some point in the week but the one in the pic above is a 70mm one iirc... I only quickly wanged a ruler across it tbh and I have the memory of a goldfish

I think the one I have is from an NA V8 S4 not a 2.7TT as there is no beading on the TB inlet... the porker one was from a turbo 911 I believe and has a lip like our 60mm TB's

<tuffty/>

 

[Dani_B19]

Leave it with me. Ive also got the TB angled aswell.

 

[Broken Byzan]

oh no, this will mean every oversize TB in the world of bay will be snatched up for 1.8t's that have no need or are not tuned to make advantage of.

 

[superkarl]

oh no, this will mean every oversize TB in the world of bay will be snatched up for 1.8t's that have no need or are not tuned to make advantage of.

i kicked myself not long ago for that exact reason lol.
some of us are worthy of it

 

[Scullies]

here's a spanner for the works, all the ebay aluminium boost piping I have seen are between 1.2mm or 2mm wall thickness.

 

[s3dave]

oh no, this will mean every oversize TB in the world of bay will be snatched up for 1.8t's that have no need or are not tuned to make advantage of.

Haha ive just snapped a 2.7 one up for £36 posted.....

 

[Jason.s]

Part number on that body you have PT fits all sorts 3.2 BKH, 2.7 ABG, 2.4 BDW, 5.2 BXA, 3.2 BPK, 4.2 BYH CNDA, 3.2 AUK, 5.2 BSM.

Audi A4, S4, A8, S8, R8 and so on..

Probably more but i cba to keep going haha.

 

[cecilthesausage]

I got 75mm one and Sem manifold yesterday

 

[s3gazz]

Iv just got this what do u think to the part number

AUDI A4 S4 2.4 V6 CONVERTIBLE 2004 MODEL


THROTTLE BODY


PART NUMBER 078 133 062B


IN GOOD USED CONDITION

 

[Andrew@A.L.D]

A pointless modification on a standard inlet manifold that doesn't match the port size of the throttle body, mapping is also recommended to scale it in.

 

[Broken Byzan]

Andrew has hit it on the head.

It's not until the restriction/backlog is the TB it makes any odds.

When mine is alive I might try the VR6 one i have @ 65mm to match my piping etc on my A4 LP mani

 

[s3dave]

My S4 70mm one has just turned up will it idle ok as is?

 

[Andrew@A.L.D]

It might idle ok if your lucky

When i first fitted my R32 T/B i used a adaptor plate on the standard inlet, the plate tapered down to the standard throttle body size. During its early days of mapping i didn't gain anything until i fitted my inlet manifold with the excessive plenum that has a 80mm ish opening

 

[s3dave]

Yeah i will open it up, unfortunately i think i have run out of time as it goes to Nicks on saturday..

 

[s3dave]

Just rebored my intake and fit the 70mm TB...Hmmmm What have i done it sounds like an harley davison, rough tickover, poping and banging....

It revs so freely now, but can this be sorted with the remap or could it be faulty? im gonna have to nurse it down to r tech tomoz, i cant even swap back because of the bore size now...

 

[Dani_B19]

Shoudlnt be like that dave. Mine idles spot on, have you reset it?

 

[s3dave]

Yes reset it what TB have you got?

 

[Dani_B19]

V6 one from a 4 motion and ive got the inlet manifold ported to suit the tb, to step down etc and im using a adaptor plate to alter the bolt pattern, only thing is mines tilted due to the bolt holes, wonder if that makes a difference?

 

[s3dave]

Anybody know where i can get a 75 - 63mm reducer over the counter tomoz!! the one i ordered is crap made out of rowndtrees jelly or something

 

[Dani_B19]

Im using a 76-63mm elbow from ap motor sports and fits spot on, also their based in dewsbury i believe so you could drive down first thing mate. My mates done that a few times to get out of a sticky situ when he needed his car asap.

 

[s3dave]

Ahh nice one Dan ..enroute... got the address?

 

[Dani_B19]

Pass matey, google them, its them who are on ebay and do the mrsilicone stuff too.

 

[s3dave]

Yeah got it.. not open saturday going by there website..

 

[s3dave]

ok ordered one of their website, also bought another 70mm TB just in case,

 

[superkarl]

Can you 2 take some internal measurements and also share part numbers?
So i can include this in my first post, keep everything anyone would need in there.

 

[Dani_B19]

I meant todo it yesterday for you karl but me and the car fell out big time and arnt talking.

 

[Westy]

Great thread Karlos.

I wonder what gains can be had with a K04. Surely going too big with the TB won't help a little blower! There must be a calculation between turbo and TB. Obviously the old 2.7 Bi Turbo S4 ran 2 K04s but also had a bigger engine that could process more air.

 

[superkarl]

Great thread Karlos.

I wonder what gains can be had with a K04. Surely going too big with the TB won't help a little blower! There must be a calculation between turbo and TB. Obviously the old 2.7 Bi Turbo S4 ran 2 K04s but also had a bigger engine that could process more air.

obv with a bigger turbo there will be more gains.
bigger turbo = more volume of air for any given PSI.

however, i think its still just as important no matter what the blower, to keep the boost/intake system as uniform and unrestricted as possible. You keep it nice and uniform in cross sectional area into the plenum, and you can know that its efficient, and you are getting the most out of what you have got. Therefore i think someone with a setup like yours should look into a larger one, and perhaps a plenum too. Obv the gains wont be as extreme as someone with a GT30, but given the low cost of throttle bodies (prior to this thread lol) its worth a shot.

i think, if like yourself who is using 2.5 inch pipework right? there will be pressure difference pre-TB to post-TB. there has to be some restriction there due to the area differences.
People might argue that going smaller at the TB will increase the speed of the flow, but its a highly pressurized system and i dont think that will be the case. If anything there will be more turbulence in the plenum.

All speculative of course.