porting the 58mm throttle body

markv

I've ported my spare 58mm TB I had around. As I bought it cheap I thought I'd take it to the max porting wise and see what happened. So this was it before I started:

Normally, when the butterfly is in rest it allows for some air to pass through. In case of a failure of the throttle, it will go to this position, the ECU will go into limp mode and it will run at something like 1500-2000 rpm. To control the amount of air in this position are a couple of humps. So I decided not to care about this mode of operation and go for maximum flow. I did (ofcourse) keep the humps that are in the throttle body so it will completely close when the buttefly is shut. So changes made:

removed the big humps front and back of the throttlebody
made a tapered entry and exit (trying to go for a bit of velocity stack idea)
removed the butterfly valve from the throttlebody and made two knife edges, reducing the profile
flattend the center rod
rethread the screws to M4 and fitted countersunk screws (secured in place with loctite 270, not taking a risk here 🙂 )

So I ended up with something like this:

Looks like it should allow for the air to pass through better 🙂

Some might have read that I tried the 68mm TB on my car and that is failed with the ECU logging code P1514 (manifold pressure is higher then expected by the position of the throttle). This happens because the 68mm TB flows a LOT better then the 58mm. When I put my original 58mm TB on, I never saw that fault code again (even did a track day).

Results with this TB are that throttle reponse is like the 68mm TB. It reacts MUCH quicker. Haven't done any checks to see if there is any change in top end power. After driving for a bit I did get an ECU light on with the ECU going into limp mode again. Reading the fault code it was the P1514 again 🙁.

So two positive things about this:

The porting of the TB actually works! It is flowing so much better now it even logs the P1514 code!
When the ECU when into limp mode, the engine actually still did 1500rpm. So no big problems with removing those humps in the TB 🙂

So nice experiment, but really need to change some things in the ECU to work effectivly with this setup. Shame, because the throttle response is very nice 🙂

Mark

vocky

you have done a fine job 😃

your ecu is quite strange with it's P1514 codes notsure.gif

markv

vocky said:
you have done a fine job 😃

your ecu is quite strange with it's P1514 codes notsure.gif

Thanks 🙂

Ohwell, the p1514 sounds quite logical. Seems there just is such a table in the ECU. You probably never ran into it because you made all the changes after cams/valves, which should lower the pressure inside the manifold..

Cheers,

Mark

Maik

Nice work Mark! 😉

Have you encountered the P1514 code only once now, or already multiple times?

alanoo

Mark ? maybe an idea ?
Do you use the MAP sensor supplied with the 2.4 manifold or your stock one ?

blue_se2

Good thinking alanoo

markv

Had the p1514 last weekend, haven't driven the car since (have to sort out issue with the ELM reader not connecting before going into traffic again).

I have both used the stock MAP sensor from my original manifold and the one delivered with the 2.4 manifold. Didn't notice any difference when the 68mm was on there. Haven't bothered to swap it when I went back to the 58mm TB.

Mark

blue_se2

After seeing vocky can fool the ECM into thinking the EGR valve is there when it is not with his EGR cheater

I know nothing about electrical systems but is there any way you could put a risistor in the wire so the voltage is lower/higher fooling the ECM into thinking the pressure is lower according to throttle possition??

andyroo

It just needs a remap doesnt it?

markv

Fooling the ECU in this case would be tricky with external electronics. As it has a table which defines what it actually should measure for a given throttle position, you would have to alter the real measured pressure value. However, that is exactly what the ECU uses to determine the air/fuel mixture and probably some other stuff. So that would not be handy 🙂

A remap where this table could be changed would be the best solution.

I've gone back to the default throttlebody now, unfortuantly 🙁. Really mis the crisp throttle repsonse I had with the ported one.

Mark

vocky

do you think it could be the remap you had done causing the problem notsure.gif

markv

Have been thinking about it, but I wouldn't know why they would have wanted to change that table. I'll see if I can find a victim to try my TB's on... (Maik!!!! 😉 )

Mark

vocky

now you're beginning to think like me, a nice unsuspecting victim to test your projects on :shock:

:lol:

andyroo

vocky said:
now you're beginning to think like me, a nice unsuspecting victim to test your projects on :shock:

:lol:

I'm quite happy to be one of your victims 😃

vocky

andyroo said:

vocky said:
now you're beginning to think like me, a nice unsuspecting victim to test your projects on :shock:

:lol:

I'm quite happy to be one of your victims 😃

I used the wife's vectra for a few years, she only complained when I removed all of the mods :lol:

ANARCHY

Just about to have a look at this, was gonna just have a look round the engine see what needs doing, take off the throttle body to make sure all the bolts undo etc. does it fit straght back on, no new seal or gasket or owt required?

andyroo

ANARCHY said:
Just about to have a look at this, was gonna just have a look round the engine see what needs doing, take off the throttle body to make sure all the bolts undo etc. does it fit straght back on, no new seal or gasket or owt required?

Bolts should be fine, and yes it just goes back on again with the old rubber gasket. Good luck with the porting! I found it to be quite theraputic :oops: dunno.. 🙂

ANARCHY

Well I failed at the first hurdle! One of the bolts was stuck, well a nut, there are three bolts which came out and one nut on a extra long stud which is now soaking in WD40.

Also how do you take the plug off?

andyroo

ANARCHY said:
Well I failed at the first hurdle! One of the bolts was stuck, well a nut, there are three bolts which came out and one nut on a extra long stud which is now soaking in WD40.

Also how do you take the plug off?

The plug took me a while too! In the top centre is a gap with a plstic triangle in it. Push the triangle down pull the plastic on the edge thats the same colour as the triangle away from the plug. A small peice of plastic should come out. This then allows you to pull out the plug.

The nut doesnt come off, just unscrew the whole thing like the rest of the bolts! Its just a bolt with a long bit sticking out. Dunno why!

Andy_Z22SE_SRi

On mine the bolt with the long threaded portion on the head was to hold a bracket on which in-turn held a few wires to it. If you have rounded the top nut off, try getting a ground-down spanner (10mm) under the bracket to undo the bolt from the tb dunno..

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