Stock 4efte throttle body limitation

i've been doing some reading on a few forums in regards to a number of matters.
as part of my searching, i've come to recognise that quite a few people ask questions about upgrading or changing the stock 4efte throttle body to something bigger ---4age, 3sge, 5mge, etc...usually in the range of 55mm, 60mm, 65mm or even 70mm

now i know the stock throttle body is 50mm, which seems a pretty reasonable size

1) can someone tell me when the 4efte 50mm throttle body will become a restriction??---maybe flow rate (CFM) and power wise

2) what is the highest hp you have seen on the stock intake manifold and stock throttle body??

3) at what point do you think its necessary to upgrade the stock throttle body? and even manifold for that matter?..as some people do these as a combination upgrade

hopefully we can get some good discussion on this one for the site members and EP owners in general...probably get some myths busted:cool:

as usual, all comments welcomed
 
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Ted

Member +
spuddy made over 400 with the stock one, i guess a large enough turbo will just bully the air in there.
 

hardcoreep

Member +
1) can someone tell me when the 4efte 50mm throttle body will become a restriction??---maybe flow rate (CFM) and power wise
That I don't know

2) what is the highest hp you have seen on the stock intake manifold and stock throttle body??
298 nigh 300whp. Some guys swap to a 4AGE butterfly, but that kinda just alters the powerband with the same numbers. Looking at the HRF car it would be obvious that once in the 400 range both need to be upgraded.
 
yeah, i've seen 300 - 320hp on the stock set up

hey thanks Ted,
any idea of approximate whp for spuddy...i forgot he is making some huge power on the stock system as well

yeah hardcoreep, how does the 4age TB alter the power band?..does it push it up, skew it lower or higher in the power band?
i even seen a post where someone ported the stock 4efte throttle body and put the 4age buterfly in it, effectively makeing it 54/55mm---which is relatively easy to do as a cheap upgrade

i suspect in excess of 300/350whp is where the stock TB becomes a bottle neck

but spuddy is doing well with his still


i'm just curious as to why people want to upgrade at relatively low power levels
 

spuddy

Ulster Area Rep.
385whp mine came in at, though I'm dumping in nitrous after the TB, without nitrous in the equation it made 387@fly (not sure on the wheel figure)

One thing that we did notice on mine was from 430hp-439hp it was very very hard to get increases and can only assume there was a flow restriction at this point, this could have been the intake or the valves.
 

GTti

Member +
This is a common issue for GTti owners (35mm OE), although I have a 55mm MR2 throttle body. Increasing the size of the throttle body and plenum neck significantly reduces the restriction in that area when using a larger compressor.

In saying that 50mm is not small I wouldn't imagine the OE TB to cause a problem for the 4EFTE. Does the plenum neck reduce the size further or does it match?

A guy in the US (http://www.maxbore.com/) can bore OE items for an extra 4/5mm for less than the same work in the UK.
 
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thanks spuddy...that's a lot of power
if i'm conservative and go with your 387bhp excluding NOS (estimated 323 - 352 whp depending on your conversion factor), then the stock TB holds up pretty well
this is consistent with what i've seen 300-320whp and what hardcoreep has mentioned

hey gtti, yeah i saw in a couple posts that u upgraded to 55mm from the 35mm...iirc, it was basically a direct swap for you....
and i've seen you mention that website as well...i checked it out, their work looks very good
in your case i can see the need for the upgrade, as 35mm is relatively small
from my memory, the plenum neck is the same 50mm as the TB...i can double check that over the weekend if you like
 

pc18

North West England Area Rep.
my mates gt has a stock engine with a vf28 running 1.09 bar. its got krissybs custom racetech inlet and bigger throttle body (i think its 70 or 75mm) emanage ultimate running a tad rich and its making 252bhp atf. unfortunately we didnt get a figure with the stock inlet and tb. this isnt much use without a figure with the stock inlet but i thought it was worth posting.
 

AdamB

Member +
Only really worth upgrading to bigger if it's going to be used for racing. I don't think that a throttle body at 65-70mm would do a road car any good, it would be really lazy. Air will travel faster through a smaller diameter than that of a larger size.
 

jam

Member +
Only really worth upgrading to bigger if it's going to be used for racing. I don't think that a throttle body at 65-70mm would do a road car any good, it would be really lazy. Air will travel faster through a smaller diameter than that of a larger size.

Hi,I think you wrong mate. TB its like a gate it will allow air to enter your engine so the bigger it was the more air will pass through. intercooler pipping is another story.anyone please confirm this.Thanks
 

artmull

Member +
What I have observed which is a comparison between the stock/standard internals 5EFHE here in the States, CR 9.8:1 and a few 5EFHE in the Caribbean using the 4EFTE pistons, CR 9.0:1, there is a difference in the amount of torque produced. One car in particular in the Caribbean made 280WHP and 260 LB/FT using the 5EFHE/4EFTE pistons with a 4AG TB. Against a car here that made 298WHP and only 240 LB/FT using a 70mm TB. Personally I think a 70mm on the 1.5 is too large unless it is an out and out drag car. I have a 65mm TB fitted to my turbo 4AG and when I had the 25G turbo on, it was very flat below 4K RPM. Now with the T3-T4 fitted the car feels like it has more torque between 3K to 4K RPM. This is just a seat of the pants observation as my car has not yet been to the rolling road/dyno and is only running 12PSI. We had a standard internals 4EFTE here around 7-8 years ago that was fitted with the ACIS Intake and a 3SGE TB that made 261WHP at 21PSI on C16 race gas. The car ran 13.0 on the 1/4 mile with 17 inch wheels and street tires and an open diff.
 
my mates gt has a stock engine with a vf28 running 1.09 bar. its got krissybs custom racetech inlet and bigger throttle body (i think its 70 or 75mm) emanage ultimate running a tad rich and its making 252bhp atf. unfortunately we didnt get a figure with the stock inlet and tb. this isnt much use without a figure with the stock inlet but i thought it was worth posting.

all comments welcomed
it may come in handy for comparison purposes
 
thanks artmull, adamb and jam

well it does seem like 65mm to 70mm may be the size to go for in an all out drag/race application...and even then i'm not sure if its necessary

reasonable upgrade sizes seem to hinge around 54mm to 60mm, whereby 60mm to 65mm maybe best for those really chasing the big power

in a lot of cases the stock 50mm TB seems adequate for the average build, in combination with the stock intake or 5efhe intake (if set up correctly)

i must say there is nothing wrong with persons building/inventing/researching bigger TB and custom manifold set ups, as this is how we learn stuff....plus a few persons have the resources available to do it cheaply or free,,,so it really costs nothing

however, sometimes it can get to the point where its gone overboard
 

AdamB

Member +
I think that between 54 and 60mm would be ideal for those road cars chasing a bit extra power. But any bigger than that I'm sure the car would be be become lazy off boost, this coupled with a larger more laggy turbo would
not be good for street use.
 

ep82white

Member +
4age and 3sge throttle body are directly bolt on at 4efte intake manifold? or they need modification to fit at 4efte plenum?

I have see at ebay that 4age throttle body are very cheap comparing to CNC billet universal throttle body.....
 
4age and 3sge throttle body are directly bolt on at 4efte intake manifold? or they need modification to fit at 4efte plenum?

I have see at ebay that 4age throttle body are very cheap comparing to CNC billet universal throttle body.....

no they are not a direct fit...modifications are needed
 
well not any "bigger" direct replacements
i guess you may have to get a rebore done and fit a larger butterfly to get a direct replacement, like gtti mentioned earlier
 
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