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MG TD TF 1500 - Advance Curve

Can those of you with TF1500 tell me what advance curve you recommend? Advance at idle, and max at what RPM? I'm fully familiar with XPAG but have limited experience with XPEG.
Steve Simmons

I wouldn’t expect it to be any different than an XPAG since they are essentially the same engine except for the bore size Initial around 10° but the total advance should be around 30-32° at 3500 rpm. But that is dependent on your CR and fuel used if you are experiencing detonation then back off the total advance until detonation ceases
W A Chasser

I assumed it would be similar if not the same as XPAG, but a rebuilder told me 15 at idle and 34 at 4K would be best. So I thought I'd get opinions since this seems a bit off to me. I've never found more than 8 at idle necessary. I typically run 7-8 at idle and 32 at 3.5K.

Unfortunately I have no idea what's inside the XPEG in question. I'll get compression numbers and bore size but beyond that who knows.
Steve Simmons

Jeff at Advanced returned my TF1500 with instructions to use 10-12deg BTDC at idle.

I believe the curve is his recipe and as such not available.

I believe it tops out at about 32 at 3,500RPM.

It runs very well now that he worked his magic.

Peter
P G Gilvarry

A lot depends on what gas formula your using and that is something we have no control over. Sure we pick the highest octane show on the pump, but what comes out the other end is a gamble, summer mix, winter mix, ethanol, non ethanol, one is never sure of what we're getting. Even though we have our settings where there supposed to be, another brand of gas, especially when out touring and filling up with another brand things can change. I try to use the same brand, but sometimes that's not possible. Here Conoco pumps have separate hoses for ethanol and non ethanol, so you're not getting leftovers from another blend. Tough row to hoe at times. PJ
PJ Jennings

http://www.mg-tabc.org/library/distributor.htm
Note RPM & Advance are distributor values
X 2 for crankshaft RPM & advance degrees
Len
Len Fanelli

The chart on the TABC site is for stock curves, which were designed for a very different fuel than we have today. Timing was set to BTDC. What I'm looking for is what curves 1500 owners have found to work well with modern formulations. Sounds like it's basically the same as XPAG.

Peter, I had one distributor rebuilt by Jeff S. I could give you the curve he used if you need it. Figuring it out is very simple, just put a timing light on the engine and check the timing at various RPM. You can also look at what weights and springs are in the distributor. I could be remembering wrong but I think the initial timing he suggested was far less. He could have changed his mind since then. I'd have to look it up again to be sure. Personally I've found that timing in the mid teens at idle is too much. The idle is never smooth. Obviously it depends on a lot of factors including cam, compression and fuel mix.
Steve Simmons

The issue with static timing before top dead center is that with the inertia reel starter bendix / drive gear starter on these cars the starter drive gear may kick back / disengage.
It seems like a recurved distributor can not be recurved for 0, or TDC static and 10 BTDC @ 1000 RPM, and still have the proper curve performance.
Here are 2 of the 16 adjustable curves for CSI ignition T type distributors: Stock XPAG XPEG
0 static, 10 degrees @ 1000, 28 @ 2000, 38 @ 4000.
For Modified XPAG XPEG
0 @ static, 10 @ 1000, 26 @ 2000, 40 @ 4000.
Many CSI ignition distributors in stock!
Len
Len Fanelli

Steve,

I was relying on my memory again, should not do that.

I just found the bag it was in, and his recommendation is 12-15deg BTDC at idle. Sounds lie a lot, but if I recall i used a little more than 1/4" BTDC as a static setting. I then verified it at idle to be within his recommendations, if anything towards the low side.

It starts great, runs great

I try to get the idle below 700-750RPM.

I can't imagine there was a lot of difference between XPAG and XPEG curves, but then I don't recall ever adjusting the timing on my TD, it worked so in good Aussie fashion I did not mess with something that works.

Peter
P G Gilvarry

Len, I've never heard of such an issue. Pretty much every XPAG distributor, in fact pretty much any vintage car distributor has been recurved for modern fuels by now and idles several degrees more advanced than original. If modern fuel burns "slower" than those of the 50's, then advancing the timing should allow it to start smoothly, not kick back. Unless I'm missing something here?
Steve Simmons

Agreed Steve, most MG engines won't kick back till you're at 18 degrees +
I tend to modify distributors so that they idle at 17 deg. and don't start advancing till 1000rpm and then full advance of around 32 deg at 33-3400 rpm, 3500rpm at the latest--The rate of advance from the 1000rpm mark is determined by the size of the camshaft and also by the compression ratio, but the fuel octane rating matched to the comp ratio makes the compression ratio less of an influence on advance curve choice compared to camshaft choice----With a std cam you just need a gradual linear increase in advance from 1000rpm-to the 3400rpm mark but with a highly modified cam the advance can be more aggressive from the 1000rpm mark and flick up fairly quickly in the lower revs but still peak out around that 3400rpm mark.
I'm sure others won't agree but it works for me
willy
William Revit

Interesting numbers Willy, thanks. The only thing I've found different is having so much advance at idle, but obviously my engine will be different than yours. My idle goes lumpy when the advance gets that high.

I'll proceed with the XPEG in question the same as I would with an XPAG. Thanks all!
Steve Simmons

Steve-i should have said, these figures are with the engine running and checking with a timing light, the 17deg idle might be a smidge less if checking static--
William Revit

That's always how I check mine. I time my engine at 3500 (or wherever full advance is), then check idle. In my opinion it doesn't really matter what the timing is when the engine is off, it's under load where it needs to be right!
Steve Simmons

Agree Steve--And also, it always pay to give it a good rev when you're done to make sure there's not another truck load of advance left in the dizzy further up the rev range, I've seen dist.s with over heavy springs fitted and you can set them up and all looks good but it was only using the primary spring and when you give em a good rev there's another heap of advance that springs up high in the rev range--nasty--always give it a good rev to make sure there's nothing hiding in there-
I doubt I needed to say this to you, but others reading this mightn't be checking for full advance and just doing the 3000rpm thing
Cheers
willy
William Revit

Just an update, we changed from the XPAG recommended curve to the XPEG recommended curve with no other changes. The improvement in power is dramatic and really surprised me. The car now accelerates up hills in third that it simply maintained speed on before. I didn't think it would make the difference that it did. I don't have the exact advance numbers handy at the moment. Set timing to 9*BTDC and got a slight ping so nudging it down to 7 or 8.
Steve Simmons

I use curve 11 on my TD and TF1250, works well.
B W Wood

I had my D2A4 (6037) distributor recently rebuilt professionally. Bit like Peter, they set it up for 10 deg BTDC and I worked from there. It is a steep advance curve as Bob Grunau's original data set shows. Fuels are different now, however. I look for maximum advance about 3500 rpm and find about 32deg is a sweet spot. Any more I can get a little pinking. Goes well at that setting on our 98 octane (no ethanol) fuel.
M Hyde

This thread was discussed between 19/05/2022 and 23/12/2022

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