Detination at 7psi boost.
Turbo Mini Forums

So for a couple weeks ive been running my engine at 4psi / waste gate pressure. On hard load at roughly 4500-5000k it pinged, but I was running standard N/A dizzy. I have since bought a boost controller to up the boost to 7psi and changed the dizzy for a Metro turbo one and set to 7deg bftd at 1500 rpm vac pipe diconected and pluged. Changed the plugs to BPR6ES ones. Still getting det.

The only thing I don't know is what ounce the dash pot spring is. It came from a supposed turbo carb but its silver in colour and I cant see any yellow paint on it.

If this is a high boost one would this cause a lean off at standard boost pressure?

Cr is 8.8:1 no intercooler. Fpr was set at 3.5 psi. Its a N/A carb converted to blow through and using the T piece trick.

If the spring is at fault, could I use two red springs instead of this one till I can get hold of a yellow?

no mention of afr?

Yes i moved to the darkside

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Have you got a fuel pressure regulator and is it connected to the vac pipe work so it increases pressure as boost increases? 4psi is very low boost pressures, it must be going really lean, doubt it's ign timing.
You need to maintain a pressure difference between the the air passing through the carb and the fuel coming out the jet, if not as the boost rises it will start to push the fuel back down the jet, I turn giving a weak mixture.

Edited by Nick king on 17th Dec, 2014.

What is the advance when it comes on boost?

How is the advance being retarded as boost rises?

Why have you disconnected the vac pipe? It's the only way advance can be altered against engine load.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Definately something amiss, Shaunas runs 8psi with no intercooler with no hint of being anywhere near det.

What dash pot oil? If it's too thin the piston will rise too quickly and then pop.

VAC PIPE WAS PLUGGED TO SET TIMING. re connected afterwards.

the engine is as a standard Metro turbo would be set up.

so i have ALL the bits to make it work. as said the dizzy is a standard metro turbo dizzy, so it should be matched to the T3 compressor map.

as far as AFR goes i don't really know. plugs are brown when removed so the fueling cant be far off.

i have been running a drump valve, and so tonight i disconected the vac line to it and now it just uses the factory BOV. took it for a quick spin and the car absolutely flies boost spiked at 8.5 psi in first . pulls real hard in second at 6 psi peak. the clutch cant handle the torque in 3rd now and im not getting the boost up to 7 psi like i was before so cant hear any Det.

could it just have been my vac operated dump valve that was causing the problem?

clutch is standard but has a blue diaphragm.

is the clutch slip affecting the boost pressure as the load isn't as much due to the slip?

dash oil is 10w40

in short here you go ...................http://en.wikipedia.org/wiki/Engine_knocking

In answer to the vac line shared between the dizzy and dump valve, yes it can be a problem. I always have the vac sensing pipe separate to everything else.

T the dump valve into the boost pressure gauge.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

double post, I'm such and amateur.

Edited by wil_h on 17th Dec, 2014.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

dizzy vac line goes to the same place it would do if it was N/A, so onto the nipple just before the butterfly on the carb.

My boost controller and dump valve run from a nipple that's screwed into the brake banjo bolt head.

i should add that the car is using 95 unleaded.

so, its possible that i could be getting det due to pre ignition by a possible build up of carbon. i have had the engine run on before. but not since the turbo was installed. could running it at 4 psi on a BDD cause this amount of build up in only a few weeks?

Where's your AFR guage?

i dont have one yet, but the fueling was set at 3- 3.5% co on an mot emissions tester.

so, if the dash pot spring is the wrong ounce spring, (too strong) would this cause a lean out on lower boost than it was rated for?

It'll all be guesswork unless you have a means of checking AFR.

In the 13's at last!.. Just

Edited by Sprocket on 18th Dec, 2014.

Yes i moved to the darkside

Instagram @jdm_brett

right, so your telling me that every metro turbo that came off the production line was put on a Dynamometer and power tuned? no. they didn't have a AFR gauge stock either, they were put together the idle mixture set and bunged out the door.

so if im running everything as a standard metro turbo engine everything should be right throughout the rev range.

the only thing un known about the set up is the colour of the spring, cause it ain't got any colour on it.

if i have the wrong spring is it going to affect the mixture at a standard boost level. thats it, if yes then i need a yellow spring. if not then i need to look some where else for the problem.

im after help not criticism.

I agree, but there is lots you can do without sticking it on a rolling road.

Firstly, retard the ignition a few deg, so set it at 5 deg rather than the 7.

Then stick half a turn on the enrichment screw, if it still pinks, stick another half turn on.

I tuned my 998 this way, but by bit. But I was stopping at the road and filing the needle evey mile or so. I also had mapped ignition which meant I knew what the advance was all the time.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

yes and no,

they would have been run up on a RR and checked that everything was within limits, which would be the case nearly all the time, but occasionally there would be a reject, this would then go back for re work... not sure what this would entail, but as an example... at fords in the early 70's on the cortina line if an engine assy had a faul they would often just lob the whole assy back into the foundry!

getting O/T but this is an interesting vid, suprising the amount of checking even back in the 60's/70's

http://www.britishpathe.com/video/automati...chang/query/BMC


Your making the assuption (as already pointed out) that every thing is std metro turbo and working as it should, after 20+ years it probably isnt, plus youve got some non std stuff in there, non metro turbo carb, higher boost, even the exhaust will have an effect.

just a few thougts on what to look at,

sort that spring, red ones are 4.5 oz, yellow are 8 oz, green are 12oz,
I supose 2 reds might work... but god knows what the rising rate would be with two springs, pluss I dont like the idea of them getting tangled and possible changing rate.

check the dizzy ( as this is new to the buld and unproven) is actually doing somthing,
get a timing light on it and rev it to check the advance is changing as it should, advance sorings can get weak, or break, or the weights can get stuck etc. check the vac advance is doing what it should too, suck on it and check the timing moves. some people set the timing at 5k where the engine will be at max advance.

Nope, just did it by ear and maybe a narrowband (which is as good as guessing). I stuck it on a rr at some point in the future and it was pretty good. But I've been doing it for years so had a good idea what I was listening/feeling for.

It was the 998 cc green mini I converted in 20 hours. It was lowish boost so it was never a big risk. It was also before widbands were available for pennies.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk