Alfa Pages

[Brit01]

As some of you may know I've been experiencing some detonation issues.

I have the 6A running now on a stock coil.

I tested the car up a very steep incline yesterday and with a full load of passengers!

In 2nd and 3rd on its limit it experienced no detonation.

ONLY when I accelerate fast 3/4-full throttle I hear detonation even with a light load on a level road. (2500-3200 rpm).

Do you think the detonation is occurring due to a lean mixture under the wide throttle opening? (due to the steep hill load test showing no detonation).

What's the best solution for lean mixture under WOT? (tried bigger pump jets and just experienced bogging down)

Or the dizzy springs are advancing too quickly under fast acceleration?

Thanks
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Oggie]

Sounds more like a timing issue not fueling.
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PHAT 33

[Brit01]

I have a new assortment of varied springs coming for my bosch to replace the old ones.

Maybe the 25 year original springs have lost some of their tension and it's advancing too quickly.

That's how it feels.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

Do you know at what rpm the secondary spring comes into play?
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

Great go this useful info from our Hungarian friend on alfaowner:

[paulhide]

More than 10% ethanol in fuel will begin to cause problems with carburetion. We are due this kind of fuel from next year.
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Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188

[Brit01]

[Brit01]

New springs got lost in post!!!!

Company will send another pack. (months waiting now).

Eager to get stronger springs in as timing is just not right mid-range in revs.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

Just been for a test drive with the thicker primary spring in.

Better still. First part of the power curve is very nice.
At about 3300 rpm under WOT in 3rd I get a touch of detonation so I need a slightly stronger secondary spring (in the post). I don't want to reduce the static anymore. It just gets hot when idling.

The stronger primary spring has improved the curve definitely but the static idle is still at about 8 degrees, just a touch less in fact. Shouldn't be pinging with this and with the vacuum advance disconnected.

Soon as I get the other springs I'll install a stronger secondary spring.
Shame they aren't easily available. Eager to get this fixed.
But it was great to feel the car accelerate better today.
Overrun lovellyyyyy. How it nosedives when you lift off the power as the engine slows down the car. You just don't get that on the modern cars.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

H&H sent me another pack a week ago.
Should arrive at my office in 7 days or so.

The I can fit a stronger secondary spring in to prevent that ~3000 rpm range over-advance issue.
I hope!

Could have been carbon build up causing detonation but it only has 3000 kms on the clock since the total rebuild.
Lean air mixture maybe but I have 145 mains in which are large than the factory ones.
maybe air correctors need adjusting.


We'll see after I try the thicker springs. cross fingers
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Oggie]

I think with all the hassle you have had with your timing you would be better off with a coil pack, ecu and timing gear off the crank or 16v flywheel and sensor. You can then play with your timing till your hearts content over the whole power curve.
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PHAT 33

[Brit01]

[Brit01]

well had some feedback from GC's forum. Saying that the dizzy is most likely just fine, could be another factor.

I know I have rich main jets in. Could be that the extra rich mixture is igniting too fast before the end of the stroke in the cylinder under the compression.

I will try going back to the original 142 mains tonight and give it a spin.

New springs haven't arrived yet.

So 2 variables I can test. smaller mains and a stronger secondary spring in the dizzy.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

Factory main jets in and tested. No difference - in fact I lost some power. larger 145's will go back in.

I will try feeding in colder air to the airbox next to see if its a hot air issue.

Then the last resort will be the stronger dizzy springs.

If all of those fail I'm at a loss!!
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

I changed the filters back to the original airbox with an extra big cold air intake tube to rule out the detonation occurring due to hot air soak.

No improvement!

It doesn't occur under load at any other rpms in any gears other than the range between 3200 ish to 3600 WOT.
Mostly in 3rd, a little in 2nd but none in any other gears.

So next variable could be the secondary dizzy spring? (hasn't arrived yet!)

It has also been suggested my compression maybe a touch high if I have tried all other possibilities!!
A thicker head gasket would be needed!!
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

You know what the MON level is here in my premium 97 petrol??

83!!!

No wonder I'm getting detonation under load at 3000 rpm.
OMG! It's like I'm filling the tank with 91 RON!!

So now how to solve this!!

May have access to race fuel with a 99.6 MON rating to add to this fuel but tricky to get hold of.

water injection kit - expensive!

maybe a stronger secondary spring as mentioned before to retard the dizzy around the 3000 rpm mark may help.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

Regarding the smaller spark plug gap I was thinking about the flame kernel.

The larger the spark the fatter the kernal I believe.

If I decrease the kernel size with a smaller spark wouldn't this slow down the burning rate and possibly assist in reducing the knocking?

What can we do as I'm sure now the issues I'm having are due to the E10 with low MON here.

I'm thinking of a few things to try.

1 litre toluene
20-30ml acetone

changing the mid range rpm curve to retard more. thicker springs

and to reduce the spark plug gap - my theory here is that I have a big spark now and it lights up a bigger kernal which speeds up the flame burning.
I need to slow this down like the octane does.

Or spend a fortune on a programmable ignition system!!!

Thanks
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

FINALLY!!

Now I'm getting there. Had a 200 kms round trip last weekend.

After adjusting the dizzy spring pre-load and readjusting the static to about 7.5 degrees with vacuum advance connected, I used BP8ES plugs.

Drove it hard on the highway, overtaking, inclines at 150 km/hr etc

Small bit of detonation in 5th under WOT at high speeds.

Much much better.

Checked the plugs Saturday and they appeared on the limit of being too hot.
Maybe some per-iginition in 5th at high speeds.

Changed the plugs to B9ES (had no projected tips on me).

100 kms back on Sunday and superb!!
I will change the plugs to BP9ES this weekend.

Think I've finally solved the detonation issue by changing the dizzy curve.
Lovely to be able to use WOT in 2nd/3rd gears with a smooth raspy sound and no pinging!!

Mains are 150 also, due to the E10 fuel leaning out the mixture.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[paulhide]

Hurrah for you
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188

[Brit01]

[BigAl]

sweeeeet well done brit for persevering, it must have been very frustrating.
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x2 33 16v
pictures http://www.alfa-pages.co.uk/viewtopic.php?t=5203

[Brit01]

Great feeling to the car now. She's back!!!!

I added a litre of Toluene to half a tank and increased the static idle to just above 8 degrees

Pulls away really nicely in 4th an 5th on the motorway!

- all sweet

Will try a touch more advance to see where the limit is with 2-3 litre of Toluene added per tank.

Acetone was mentioned also.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

After having many intermittent issues with detonation I decided it was time to change the primary dizzy advance spring. A new set of 20 arrived!


A fairly simple job I had done several times went very wrong.

I needed to change a dizzy advance spring.

First circlip off, small holding pin out (most tiny part that can get lost easily), plate off, then second circlip off.

I had carefully placed the tiny pin on a cloth.
The circlip catapulted out of the special pliers and hit the small pin which flew off behind the sofa somewhere!! 1 in a million chances of ricocheting the pin with the circlip.

After 1 hour of frantically searching for it appeared! phewww (its only 3mm long and 1mm wide!)

Then putting the small 10mm bolt back on the dizzy onto the block - the bolt fell down the flywheel timing hole (wasn't sure though). Nooooo!
Removed the bottom plate underneath to see if anything fell out. nothing!
Moved the engine forward in gear to see if the flywheel was catching on it - all ok.

Ok I used a bolt from the flywheel cover from underneath to re-attach the dizzy.

Started her up and all ok. phewww

But a few metres down the road I heard a small rattle for a second - scared the crap out of me thinking it was going to get lodged or something.

After that all ok.
Maybe it fell out down the road, anyway I couldn't find the dam thing.

What could have gone wrong did today.


Final result: the new primary advance spring felt much better.
I could set a static of 9/10 degrees, full throttle and no pinging so far.
Had pinging with 7 degrees before.
The old spring was very very soft compared with the replacements I have.
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Bobkelso]

Hi Brit,
nice tuning of the dizzy
(and funny Murphy's Laws experiment )
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Alfa 33

[Brit01]