Part throttle lean off pipe.
Turbo Mini Forums

Hi Guys,
From my last rolling road session there are slight strange happenings in the fueling. I am using the normal turbo HIF44 carb with heavy spring in the dashpot plenty of oil etc etc. Runs a tad rich on tick over (not a problem) then when you first get on the throttle (about 2K) the mixture weakens off to about 10:1 AFR, as the turbo comes in and it starts to make power the mixture richens to about 15:1 AFR at the top end.
Could this be caused by the seemingly pointless piece of tube (part throttle lean off)?
Anyone had any problems with this or is it simply needle selection?

Ta very much

anything below 14.7 to 1 is rich ,and above is lean ,so your running lean at boost and rich at 2k ..hope that helps .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Lol sorry Robert.

Swap those figures. Definately rich at top end.

Rubbish advice from me ignore

Edited by Mr Joshua on 22nd Apr, 2009.

Own the day

I heard that some peeps on here block them off cos they do funny things?

I think that TurboTel found that it could be made to work, but is much more stable when this is blocked off.

Have a look at Tel's thread with his contraption to measure the position of the needle.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=159683

EDIT: I found that mine would never run properly with this connected. I would end up lean when going from part throttle to WOT. So it has been blocked off since with no further issues.

Edited by theoneeyedlizard on 22nd Apr, 2009.

In the 13's at last!.. Just

Just read that thread. Never knew you could remove that pipe. A bit miffed due to the issues I had a few years back. Thanks for posting the link

Own the day

On 22nd Apr, 2009 Mr Joshua said:
Just read that thread. Never knew you could remove that pipe. A bit miffed due to the issues I had a few years back. Thanks for posting the link

In the 13's at last!.. Just

On 22nd Apr, 2009 theoneeyedlizard said:

On 22nd Apr, 2009 Mr Joshua said:
Just read that thread. Never knew you could remove that pipe. A bit miffed due to the issues I had a few years back. Thanks for posting the link

To be 100% clear... You can't remove it. It has to be blocked off.

Own the day

Think i will give that a try this evening. As you say its basically as you go from part throttle to accelerate the mixture weakens and the engine stutters before accelerating. Just need to sort the slippy clutch out next then back to the rollers for more boost

Yep, mine would never run right with it connected - I just blocked both ends up and it ran fine from then on.

website:- http://www.terryhunt.co.uk

Jesus Tel almost blinded by the light bulb thats just gone off in my head! Having just read that explains a lot. Mine has been doing exactly that since forever, never could get the damn thing balanced. Changed carbs, needles, messed around with the oil in the dash pot.

Its as you say when I gently apply the throttle its as if the engine just vanishes nothing (motorway driving normaly) then you feel it start to drag itself back up. Feels like a masive flat spot

I just took to applying more throttle than rerquired then backing down before the thing launched down the road FFS how f ing ironiic that the pipe that caused me all my woes I dont even need.

Own the day

I had exactly the same problems, blocked off the pipe a week ago, all problems gone (although it is running a bit rich now on part throttle)

just to screw things up, i still have mine all piped up with no problems, but i'm not normal so don't mind me

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

mine is still piped up as well, works fine for me

yep me too ! it does create a drop in boost response at low rpm ,i get 2 psi at 1800 instead of 4 ,but it also gives me 42 to the gallon so im keeping it ,, its easy to block off with a solenoid for racing .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

mines on too

does there seem to be a trend? Nic was fastest at avon in class D with a carb, then matt.......

it does seem to sugest there's nothing wrong in using the part throttle lean off pipe with higher powered engines

Though at avon I can safely say there was no part throttle used

Well Shed might have apoint, maybe we should all connect them if disconected, and save the plant!
So Nic maybe i'm doing it all wrong if you didn't use part throttle

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

hahaha oops

so full throttle on a drag strip then.......well in that case expact to see no difference in my times at this years avon park

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

well its time to get a new CO metre and set the car up as per the thread in the post above. Being a little wiser now and having thought about it, I pobably bore washed the other motor to death! Luckily it was the spare old motor.

Own the day

Definately resolved the annoying problem i had. Now pulls smoothly from 1500 rpm with no coughing. Just need to install the new clutch and its back to the rollers.
So far 168bhp @ 5990 with 8lbs boost. Well happy.