Technical Uno 1100 with free-flow - performance issues... ideas?

[A_Acolyte]

Hi there eveyone. This is my first post.

A few months ago I was running a stock-standard '95 Uno 1100 FIRE.

Then I fitted a K&N Filter and there was a slight increase in torque (but not much change to the top-end).

Then, a few weeks later, I fitted a free-flow exhaust, but did NOT do the branch, just from the branch, to the bumper. There was a fairly drastic performance increase and the car sounded awesome. Then a few days later I noticed that the car was actually running very rich and, believing that that was not ideal, I adjusted the mixture setting to a more 'correct' setting.

Performance deteriorated.

So set it differently, and got some performance back - almost to where it was.

Then, today I completed the free-flow and got the manifold done too and, took the opportunity to get the car's mixture set at where it should be (as per Uno spec, at about 2%).

Performance has deteriorated. In fact, I drove my mom's stock-standard Uno a few minutes ago, and it performs much the same (perhaps better?) than mine! 8(

Mine goes 0 - 100km/h in 14 sec. There's something wrong - after all those mods, it should have more hop than that surely?! (And it did when the first part of the free-flow was fitted). (Top-end, however, is about 170km/h)

Any ideas? What should I do to get the performance that I should be getting from the free-flow system? I gather the problem has to do with my fuel-mixture.....

Any input would be much appreciated.

Thanks in advance,
Dave

 

[LuiPoland]

show some pictures of mods, or write more

-diameter of exhaust?
-lenght and diameter of intake pipe?

 

[Oldschool]

Can you adjust ignition timing?

 

[M@nticore]

Just get your car on a rolling raod, it's the best way to get your peak performance.

 

[A_Acolyte]

Did some fiddling with the mixture screw yesterday. It did help somewhat, but I still haven't got significantly more performance than I did when my car was still stock.

I am receiving SO MUCH conflicting information from guys in the industry about whether or not I need to increase the size of my jets to compensate for the cars new-found ability to push air through faster. Some say I DO need to change them, some say I don't.

Now that I know more about how this all works, it seems logical to me that they DO need to be changed - with the widening of the entire exhaust system the car can now get air through quicker (in other words it can process a greater volume of air per second), and hence, it makes sense that it'd need more fuel per second too - and that can only be attained by fitting larger jets - no amount of messing with the fuel mixture is gonna help that. (Or am I completely misunderstanding something here?).

Its interesting that no matter how much mixture-fiddling I've done, the car has always kept its top-end. Testament to the fact that the mixture screw only affects the mixture in the lower rev-ranges. Again, that shows that to get the higher top-end out of the car that I should be able to get, I'd need to be able to get more fuel into the engine at the higher rev-ranges - in other words, fit fatter jets.

However, with all this said, I'm gonna take the car to some car performance specialists tomorrow and get them to set whatever needs setting. I'll leave my credit-card at home I think because they specialise in doing turbo conversions etc. Need I say more? Hahah!

I'll post once I know more.

Thanks to those that have responded thus far!

 

[M@nticore]

your idle screw only affects your co settings for idle. the size of your jets etc is what determance the a/f ratio for the rest of the ranges eg. from idle to full throttle.
There will be no need to change your jets only when you intall a cam etc.

 

[A_Acolyte]

There will be no need to change your jets. only when you intall a cam etc.

Hmm. So what exactly should I need to set to get this working? Make an adjustment to the the mixture screw? A good friend of mine suggested that I might also have to have the timing adjusted (because with the lower back-pressure from the free-flow, he reckons it'd be necessary to advance the timing slightly... ...but he's a VW guy...).

Any input?

BTW, I'm still trying to book a session on a dyno - these dudes are so booked-up around these parts.

 

[Chas Uno]

Hmm. So what exactly should I need to set to get this working? Make an adjustment to the the mixture screw? A good friend of mine suggested that I might also have to have the timing adjusted (because with the lower back-pressure from the free-flow, he reckons it'd be necessary to advance the timing slightly... ...but he's a VW guy...).

Any input?

BTW, I'm still trying to book a session on a dyno - these dudes are so booked-up around these parts.

See M@nticores post above! The mixture screw only affects the pilot/ idle jet, which simply adjusts the CO output at tickover. You'll need to change to a larger main jet to richen the mixture as the mixture screw has very little affect on engine performance.

I doubt if adjusting the timing will make any difference unless you install a different camshaft. Stick to the FIAT settings until you get your car on a rolling road.

In fact, I wouldn't do anything until the car is on the rolling road. Only then will you get a decent mapping of the engine's fueling, ignition timing and CO output over the rev range, and only then will you know what needs to be adjusted/ changed/ replaced.

To tinker with it now is really just groping in the dark

 

[A_Acolyte]

Yeah. This is what I've been getting from EVERYONE. You're contradicting each other:

M@nticore: "There will be no need to change your jets....."

1986Uno45S: "You'll need to change to a larger main jet to richen the mixture..."

Fortunately I have a booking for a dyno tomorrow morning. I'll report on whats found/adjusted.

Til then,
Dave

 

[Chas Uno]

Yeah. This is what I've been getting from EVERYONE. You're contradicting each other:

M@nticore: "There will be no need to change your jets....."

1986Uno45S: "You'll need to change to a larger main jet to richen the mixture..."

Fortunately I have a booking for a dyno tomorrow morning. I'll report on whats found/adjusted.

Til then,
Dave

Sorry Dave, what I meant was that IF you want to richen your mixture, you'll have to change the main jet and NOT rely on adjusting the mixture screw.

But before you decide to put in a bigger main jet, you need to have the exhaust gas analysed on a rolling road to see if you need to do this or not.

Hope this makes it clearer, and good luck with the rolling road session tomorrow.

 

[Oldschool]

Hmm. So what exactly should I need to set to get this working? Make an adjustment to the the mixture screw? A good friend of mine suggested that I might also have to have the timing adjusted (because with the lower back-pressure from the free-flow, he reckons it'd be necessary to advance the timing slightly... ...but he's a VW guy...).

Any input?

BTW, I'm still trying to book a session on a dyno - these dudes are so booked-up around these parts.

In post no. 3 I asked you whether you can adjust the timing. It wasn't clear then whether you have a carb or ECU controlled.

The Uno backbox is a terrible restrictor. When replacing it it and improving the air intake you obviously get more air into the combustion chamber. Increasing the volumetric efficiency requires more fuel. But it is evenly important to adjust the timing. This needs to be done with the help of a gas analyser.

 

[A_Acolyte]

Hi guys.

Ok, this WOULD happen to me, wouldn't it? The place I took my car to specialises in performance-tuning (all the owners being heavily involved in the local racing scene etc). With that said however, get this: My car didn't fit on the dyno. Why? Its dropped too low and the free-flow by the manifold was against the dyno's rollers! 8/

So, that promptly got me nowhere. Though they admitted to not having much experience with Uno's, I asked them to tune it without the dyno.

Turns out the cars timing was slightly advanced and, as I suspected, my random fiddlings with the mixture screw were just that - random.

So, the mechanic set the timing to what I assume to be 'right', and using the CO meter he set the CO to what seemed to be somewhere around 2.5 or so. While things are indeed better, I still feel the car isn't near where it should be - my moms car (the stock-standard version of mine) isn't far off mine in terms of pull-away performance (my torque in low revs is lacking).

Now, I the mixture screw only affects the car in the lower rev-ranges, but I stress - thats where my problems are - my top-end is just fine!

What, ideally, should my CO be reading? I see in the UNO Haynes manual it says mentions 3.5%.... that seem right to you guys?

Also, how sensitive is that mixture-screw? How much change in CO% does a 180 turn on the screw make?

Are my sparkplugs likely to be causing any of low-torque problem? I have Champion Eons fitted.

Its a real pity I couldn't get on that dyno today...

Many thanks to those that have offered input thus far - you guys have thus far been my most useful source of info...

Dave.

 

[M@nticore]

Did you fit a branch aswell or just the freeflow system.
With a branch and a decent freeflow you can only expext in the reigionof 6-8 % power extra, not that much of a differince above standart. so don't get all excited in thinking that going to get a huge power increase. you get the most power by modifiying your cylinder head, a full head conversion with modded cam will give you +- 20% increase above standart.