Tuning Uno Turbo Mk 1 – 1 bar boost – bigger injectors?

[Luckor]

Hi,

I've read some threads here about the injectors on the Mk 1 Uno Turbo. Interesting stuff. I've just restored an Uno engine that is going into my X1/9 and the plan is to go for 1 bar boost. Just about everything needed to reach this is in place, but now I've come across some 220 cc/min (at 3 bar) injectors that are slightly bigger than the original.

I've learned that I actually don't need bigger injectors to reach about 130-140 bhp at 1 bar boost. Increasing fuel pressure with a proper progressive regulator should do the thing. But running too lean is something you don't want with a newly restored engine, so ... Am I safer if I go for the slightly bigger injectors and instead lower the fuel pressure at lower revs in order to not run rich at lower speeds? Maybe a little mechanic adjustment of the air meter also will be needed, I figure.

Or is it better that I stick to the standard ones after all? They just seem so small with only a bit over 150 cc/min!

I know that an option is to install a fifth injector triggered by the standard high boost safety switch on the plenum. But it's hard to believe how this could bring a proper mixture at high boost.

 

[alexGS]

Nice well-written post there - you have obviously done your homework.

I'm not the most knowledgable person to comment on this, but I will anyway (since the others haven't replied yet). My Uno Turbo has been running up to 1 bar on standard injectors for years, including being thrashed on a track at full boost most of the lap. Therefore I think the standard injectors are sufficient unless you plan to make other mods or build a 1498cc turbo engine. For peace of mind you might want to get the standard injectors cleaned and tested by a specialist (a standard service not model-specific) - injector output can diminish over time as a tiny filter inside blocks up. Get them to supply new seals too. Were the hoses all cracked or have they already been replaced?

So that's what I'd be doing - investing in restoring the standard setup - and you'll get great fuel economy too. If you change to bigger injectors I believe the only way to really do it right is to use replacement management systems (Megasquirt or Link, etc.) and start from scratch.

-Alex

 

[Luckor]

Thanks very much for helpful answer!

I think I just needed someone to tell me that the standard injectors actually will work fine when the engine is not that much tuned. I had my thoughts earlier about getting the injectors cleaned and tested just as you suggested, and will go for that now. I will install a broadband lambda sensor with gauge so I hope it will be obvious if the engine for some reason runs lean after all.

Yes, the short hoses have been replaced before, so no cracks.

 

[lewey]

Thanks very much for helpful answer!

I think I just needed someone to tell me that the standard injectors actually will work fine when the engine is not that much tuned. I had my thoughts earlier about getting the injectors cleaned and tested just as you suggested, and will go for that now. I will install a broadband lambda sensor with gauge so I hope it will be obvious if the engine for some reason runs lean after all.

Yes, the short hoses have been replaced before, so no cracks.

Will be fine on standard injectors. My UT was bored to 1423cc and ran 1.4bar boost on 4 standard injectors at 4bar fuel pressure for quite a while.