When should boost start to come in?
Turbo Mini Forums

Well iv been having some problems with my carb where the adjuster screw didnt move the jet, so i put a re-furbed turbo carb on today took it for a spin and things seem different.

With the old carb the turbo would start to spool up at around 2500-3000rpm, but since i have put this carb on the turbo spools up straight away from about 1500-2000rpm, at which point it is very low on power, but as soon as i reach above 2000 the power is back up, this is making it quite difficult to drive is it means i need to rev the engine quite hard to pull away from junctions...

Is this normal or have i got something wrong?

i dont really know what the problem is but you shouldnt have to rev it that much to pull away.
My T3 kicks in low down in the rev range but its due to a number of things, all depends on how you design the engine build.

The problem im having is the engine is right down on power as the turbo starts to spool up between 1500-2000rpm.

So to pull away im having to rev to about 3000+rpm otherwise it will stall.

With the old carb it would be off boost untill alot later in the rev range (i could happily cruze round town in 3rd or 4th off boost or pull away) but now its on boost all the time. As if below 2000rpm there really is hardly any power and the engine bogs down, then as i pass 2000prm the boost comes in as the engines got all its power back...

Edited by tomf on 25th May, 2010.

Have you put your old needle in the new carb??

No the new carbs got a new BDD fitted...

I didnt realize the carb could effect when the turbo spools up.

mixture affects power, power is related to how much expansion there is form the combustion, the expansion drives the turbo ect...

Ah thats a very true point how silly o i look now lol.

I know its not a great way atall, but it was only set up using a colour tune till i can get it on the rollers, but i wont be able to get it on there for about a month.

Whats the best way to get my fueling a bit better from home? it does seem to be running nicely with this setup apart from the bogging down untill above 2000rpm.

With the old carb i was getting some a little black smoke out the exhaust where it was running rich and i couldnt adjust the fueling, but with this car i no longer have the black smoke.

well its worth poping the other needle in and seeing what happens,

and getting a wideband

Yes good idea ill try that tomorrow.

On a side note i also saw my temperature gauge go up slightly higher than normal for my journey to work (45min drive). It usually sits at about 60 but was around 65-70 today.

doesnt a temperature rise indicate a lean mixture?

Edited by MarkGTT on 25th May, 2010.

Ah a google search has just confirmed that ill play with the other needle tomorrow and rirchen the mixture up a bit.

I think retarded ignition can also cause hotter running temps too.....

To be honest Tom, I woulnd't feel safe driving it around on boost at all if it's not been setup. It's just asking for you to get carried away and melt a piston!

Mr. Prawn, the friendly Crustacean- slowly making steps towards forced induction.

Well iv had a play with the fueling and timing today and iv finally got the mini running nice and smoothly (iv even got a smooth idle at 700rpm i never managed that with a distributor)

Having megajolt plugged into the laptop and tweaking things whilst your there really makes you see the difference the unit can do.

I also set my fueling up using an emissions tester, not perfect but will do untill i can get it on the rollers (btw it was running lean)

So seeing as i had it running smoothly throughout the rev range for the first time i thought i would turn the boost up from standard for the first time it certainly makes things a bit more fun, i only bled it to about 6-7psi but even that made the engine alot more lively.

wait until you crank it up to 18psi.. thats lively!

glad its running better for you.

tom im glad your getting on with this more so than i am haha. facny popping by work and showing me maybe taking me out. i wouldnt mind having a look at a few bits on the megjolt as its the only thin ihavnt bought yet

Well a bit of an odd one, i bled the boost up to 6-7psi last night and took it for a quick spin up the road and it seemed great.

But i took it for another drive today, around the lanes it seemed great, but as soon as i got onto the motorway as soon as boost started to spool up it lost all power, if i let off so the dump valve pumped then it would let me built the power up again, but would have to keep dumping the bost ever 20 seconds or so, so i pulled over after doing this about 5 times and shut the bleed valve back up a bit to around 4psi and it would run properly again without any flat spots...

Edited by tomf on 27th May, 2010.

i'd leave it at 4psi untill you get it to a rolling road or get a wideband fitted..

i know how tempting it is to wind up the boost straight away but trust me it will end in tears without a setup, mine lasted 6 weeks when i did my first conversion.

Yea i know what you mean thats why iv only just decided to turn it up to see the difference.

Dont worry it will be staying at 4psi till i get it on the rollers now.

Anyone got any ideas what it could be causing the bad loss of power though as if i take it to the rollers then find out its the FPR or something then it will be a waste of my time and money to take it there..

Wise words there from nick,
Tom pm me if you need a hand im working gravesend tomoro if yiu want me to pop over and have a ganders?

Cheers for the offer mate, but im a bit of a trek from Gravesend. CT3

Could be a heavy lean out. I'd definately be getting a wideband on there as soon as. It's probably the single best addition I've ever made to my car.

WWW.TURBO-MINI.COM

sounds like you need to block the part throttle lean off pipe.