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Throttle Bodies
Dave Bailey - 9/3/11 at 08:54 PM

I am beginning to wonder if the throttle bodies I have are too big for my 2.0 ST170..... I was given a set of 4 single body 48's but I am concerned if the bore is a little too big.... Anyone got any advice... I can get the motor to start but as soon as I open the throttle it dies... Wondering if too much air and it is running too weak.....

Dave B

omega 24 v6 - 9/3/11 at 09:03 PM

I was getting similar symptoms with my gsxr1000 bodies. They needed balanced but I also discovered a slightly bent butterfly which needed some "adjusting"

There was a huge difference once all was put in order.

MikeRJ - 9/3/11 at 09:07 PM

quote:
Originally posted by Dave Bailey
I am beginning to wonder if the throttle bodies I have are too big for my 2.0 ST170..... I was given a set of 4 single body 48's but I am concerned if the bore is a little too big.... Anyone got any advice... I can get the motor to start but as soon as I open the throttle it dies... Wondering if too much air and it is running too weak.....

Dave B


Sound like whatever ECU you are using needs to be mapped a bit better.

doddy - 9/3/11 at 09:34 PM

hi had this on mine if i turned down the fuel pressure regulater it would run turn it up above 2 and it would not rev changed my fuel pump and its sorted it out

austin man - 9/3/11 at 10:08 PM

Mapping I reckon, you will be drawing twice the amount of air in than standard I would think

zetec - 10/3/11 at 08:54 AM

Saw an article by Dave Walker in PPC a while back. He suggested that oversize TBs are not really a problem as it is the injector that supplied the fuel feed and was not reliant on air speed, in the same way a carb was, to draw the fuel into the air stream. Having seen a injector in action they squirt the fuel out rather than spray a mist, so the TB really is just an "air valve". Even so I run 45s with no issues so the jump to 48s should not be too much of an issue. I too suspect the map is incorrect, or perhaps an injector below par.

coozer - 10/3/11 at 11:11 AM

quote:
Originally posted by Dave Bailey
I am beginning to wonder if the throttle bodies I have are too big for my 2.0 ST170..... I was given a set of 4 single body 48's but I am concerned if the bore is a little too big.... Anyone got any advice... I can get the motor to start but as soon as I open the throttle it dies... Wondering if too much air and it is running too weak.....

Dave B


Mine are about 43mm and during the setup stage I had exactly the same problem. Now if I remember rightly it was due to a lack of resolution at the bottom of the map. Using tps if theres big gaps between the rows you do't get a progression away from the idle point.

What does your fuel map look like Dave?

DH2 - 10/3/11 at 11:23 AM

quote:
Originally posted by coozer
Mine are about 43mm and during the setup stage I had exactly the same problem. Now if I remember rightly it was due to a lack of resolution at the bottom of the map. Using tps if theres big gaps between the rows you do't get a progression away from the idle point.


This.
Using a large throttle means that for only a small opening of the throttle, you are letting alot of air in, which means throttle control / resolution at lower throttle openings (most of the time) is worse than using a small throttle which will give much better control and also have the benefit of providing higher air speed and therefore improved filling of the cylinder whilst the inlet valve is open.

DH2

matt_gsxr - 10/3/11 at 08:46 PM

Also some of the gsxr tps have a bit of a dead spot at the end of their travel.

so, make sure you are getting changes in tps value for very tiny openings of the throttle.

Dave Bailey - 10/3/11 at 09:42 PM

Thanks guys for all the advice... Coozer I will take a screen shot of the map at the weekend and post...

As usual great supprt from the forum....

Dave B

Dave Bailey - 12/3/11 at 09:44 PM

Coozer... If you get a chance have a look at the Map in my photo archive.... I couldn't improve on the resolution of the pictures.... sorry....

I am a bit worried about the oil pressure @ idle...

thanks
Dave B

coozer - 13/3/11 at 11:25 AM

I had similar tps values as you there. Problem just of throttle was there was no extra fuel to go with the extra air.

This setup with small grads at the bottom works OK for me.



Good luck!
Steve

Dave Bailey - 13/3/11 at 01:00 PM

Thanks steve.... I spent the rest of yesterday going over the setup again and I found that the sensor cal values in the ECU had been overwritten somehow... Must have been me at some point... The net result is that I now have good oil pressure reading plus it turned out that I had adjusted the fuel pressure to 5Bar!!!!!! I now have it at 3 bar and the car starts and will idle... It bangs pops farts and shoots flames out the exhaust when I open the throttle plus I can't seem to run it with Lambda and sequential ignition enabled but it basically runs.... I need to check that I have the crank and cam sensors the correct way round but all in all things are a bit better!

thanks for your advice.....

coozer - 13/3/11 at 01:06 PM

Mine popped and banged the same before I changed the bottom few rows.

Flackmonkey kindly pointed me towards the set up above

Steve

ashg - 14/3/11 at 11:11 AM

go and buy dave walkers haynes book. everything you need to know to get it drivable is in there.

http://www.amazon.co.uk/Engine-Management-Optimising-Carburettors-High-performance/dp/1859608353/ref=sr_1_12?ie=UTF8&qid=1300101022&sr=8-12