Ignition timing for 97 Octane fuel - xflow.

[Tim_H]

I always run my cars on Optimax, (or SUL).

 

Question is,

Is my 1600 Xflow (1996) ignition timed (at the factory) for Std unleaded?, as I think it states in the build manual - and is it re-mappable for SUL?, and what should the timing be set at?.

 

Bearing in mind, the last time I used a timing light on a Xflow was 20 years ago!.

Please refresh my memory, IIRC. -

1)The timing light goes on plug #1.,

2)The timing marks are identified and on the flywheel with Tip-ex., (behind some cover on the bellhousing).

3) There is no vacuum advance on my 7 to disconnect?

4)Slacken off the distributor

5) Rev to say 1000 rpm, and adjust the timing to correct degrees BTDC?

6) Tighten distributor.

 

or am I too old fashioned for all this.? 😳

many thanks

Tim

[Joe 90]

There are a lot of unknowns, so I can't give a complete answer. If you search techtalk you will find this has been covered extensively.

 

As a starter though, 12 degrees at 1000 rpm is the usual setting. The timing is done on the front of the engine, not the flywheel. Tipex the mark on the pulley and read off the front timing chain cover.

 

SEP field working, not spotted in 103,100 miles. Some photos on webshots, updated 25 Jan

[Roger King]

1) Correct

2) The marks are on the crank pulley and front cover

3) Correct

4) Check timing first in case it is already correct

5) Should be set at idle - around 900rpm

6) Yes if you had to adjust it

 

Caterham quote 14 degress btdc at idle. This is for one of their own engines with their own distributor. Anything else will be different. If you set it to this figure, you will only see around 25 degrees btdc at 4500rpm, although the engine really needs more like 35 degress btdc. The only way to get this is a different distributor which will release around 8bhp extra. Do not set the timing to 35 degrees btdc at 4500rpm with the original dizzy, because you will have way too much at lower revs.

 

You don't need the 97octane fuel for your current dizzy, and probably don't even need it with a dizzy that has the correct advance curve.

[Tim_H]

Thanks both. *thumbup*

 

So is it 12' or 14' BTDC at idle?, and is that for normal unleaded?

 

*idea*I was of the (probably misguided) opinion that the higher octane of Optimax would combat any pinking, if the timing was advanced more, and also that the 1600 has quite a high Compression ratio?

 

and yes, I could release more power.

 

Remember in the days, when (std)unleaded was first introduced, and real 4 star was still available, basically the population was brainwashed into retarding their ignition to save the planet with green fuel - not realising that you lose power by doing this, andmake the engine run less efficiently, and economically.

 

was all this (ignitition retardation) purely an effect of the lack of lead in the fuel, or because Std Unleaded has a lower octane than (real) 4 star.?

 

So back to my question, - If I time the engine for SUL, do I gain power over the factory settings, that appear to be geared towards std unleaded?.

 

(this all only makes me wonder, because my previous Cosworth had a separate setting for SUL, and normal unleaded, which involved removing a resistor near the ECU.)

 

thanks for reading - long winded I know.

Tim

 

Edited by - Tim_H on 3 Mar 2005 15:45:12

 

Edited by - Tim_H on 3 Mar 2005 15:46:06

[Joe 90]

Roger knows more about XFlows than I do, so go with his suggestions.

 

SEP field working, not spotted in 103,100 miles. Some photos on webshots, updated 25 Jan

[Crudders]

As Roger says, you need a distributor designed to run on higher octane fuel to get the benefit. I run an Aldon distributor - 10 degrees static advance, 35 degrees @ 4000 RPM - with Castrol Valvemaster Plus, which is a lead replacement additive with an octane booster. As Roger suggested though, when I've run out of Valvemaster and run it on 95 Octane regular unleaded, it hasn't complained.

 

The X/F Aldon distributor is about £100 IIRC.

 

Crudders

[Graham Sewell]

Ot hey will remap your existing dizzy for around £60.

 

Low tech luddite - xflow and proud!

[Tim_H]

Ot hey will remap your existing dizzy for around £60.

 

Interesting. Thanks - Who's that?

 

Tim

[Graham Sewell]

Aldon. They take 1 to 2 weeks to recalibrate your dizzy to your requirements. tell them what engine, camshaft, fuel, valve sizes and anything else and they'll do it up for you. One of the cheapest upgrades I have ever done.

 

FYI - look under services (Rolling Roads) for a little info; and then call them for a chat over the specification.

 

Low tech luddite - xflow and proud!

 

Edited by - Graham Sewell on 4 Mar 2005 13:35:22

[Tim_H]

Just looked today @ the distributor. - It's an Aldon one, but no sign of any identifying number though. (Lucas stamped into it) - is this the baby then?

 

Re- looked at the manual, and it's slightly contradictory in places. It says that the CR for my 1600 is 9:1, which is relatively high, and says to run it on 4star, 97 ron.

 

Elsewhere it states that it can run on unleaded. (now this being 1996, SUL wasn't around IIRC.), so I presume it means the 95? RON stuff.

 

even more confused than before

[Graham Sewell]

What Caterham did in those long ago days, was to modify the ignition curve to retard it a lot to prevent detonation. They did not however put hardened exhaust valve seats in. So yes, it was safe to run 95RON unleaded for short term necessity, but prefered 4* leaded to protect the valve seats.

 

The problem was that they were overcautious with the ignition curve and this is where Aldon can release some cheap horsepower at sensible prices. But a long term solution would include the valve seats as soon as any noticeable tightening of the tappets is observed.

 

Incidentally, super unleaded has been around since the mid 80's in the UK as I used it in my Opel Manta as I did not want to retard the timing and lose the power that was designed into the engine. In those days it was also cheaper than 4* and all GM engines since 1985 had hardened valve seats.

 

Low tech luddite - xflow and proud!

[Joe 90]

9 to 1 compression isn't that high. My Xflow must be on more than 10 to 1 and doesn't need more than 95 octane unleaded (it has got hardened exhaust seats though). Of course compression interacts with valve timing as far as octane requirements are concerned.

 

SEP field working, not spotted in 103,100 miles. Some photos on webshots, updated 25 Jan

[Tim_H]

uh, oh., so will my '96 engine have hardened valve seats?, or not? , or will I need to use a fuel additive.

And what's to be gained by using 1300 pistons?, I've read that this raises the CR to 10.5:1.

 

is there any power to be gained by that mod alone?

 

Edited by - Tim_H on 8 Mar 2005 08:00:01

[Joe 90]

Unless you look inside, you can't tell whether you've got hardened valve seats. As I'm not a big fan of aditives, my own personal choice would be to run it on regular 95 octane unleaded and keep an eye on valve clearances. If set recession gets bad, then go for a proper upgrade with hardened valve seats and forged pistons. Piecemeal upgrades cost money but don't neccessarily give the expected improvements unless you've tackled all the weak spots.

 

SEP field working, not spotted in 103,100 miles. Some photos on webshots, updated 25 Jan