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MG TD TF 1500 - Dyno Experience Wanted

A customer who has bought one of our superchargers (mgtrepoair.net) is planning on getting his car on a dyno, and I realize that I don't have any first-hand experience with the subject.

Can anyone who has done this with a T-type please comment on the procedure, what the testing found, and what variables (plugs, needles, timing, etc.) needed to be tweaked in order to maximize performance?

Thanks very much.

Tom Lange
MGT Repair
t lange

Tom. I would contact Steve Baker in the UK as they have synod a few of their SC'd cars. I believe you can find several of their runs on YouTube.

Bill Chasser
W. A. Chasser Jr


Joe, read this article about Dyno tests if you haven't already. It will at least provide some areas to decide on what you want to achieve and help narrow the variables. http://www.mossmotors.com/SiteGraphics/Pages/dyno.html
Richard Cameron


more to look at: http://www.chicagolandmgclub.com/driveline00/1102/tune4spd.html
Richard Cameron

Tom, I did a pre blower run just so I would have something to compare to. I wasn't looking for a tunning session with the blower but I did remove the damper springs just to see what the A/F would do. If I was looking for a tune session, I'd bring a wrench to use to change the timing, some heavy and very light oil to change out in the dash pots and some different needles. This is assuming that the dyno shop has a tail pipe sniffer so you can see what you are doing. A dial back timing light would be useful as well.


Just my two cents worth
MG LaVerne

Thank you, all - those references and experiences are exactly what I was hoping to learn from.

Tom Lange
MGT Repair
t lange

Invariably, people think they need richer needles after modifying the XPAG for more horsepower. I once went (at the request of a client) to a dyno session with 7 and RO needles to try in place of his LS1 needles after extensive cam, head and piston work, and H4 carburetors. In reality I should have brought GJ needles. The engine ran with the 7, after considerable leaning, but it would not make top expected power. It didn't run much better with the LS1

After the session, on the road, we put in the GJ needles, and the 'butt' dyno showed them to be a better match... which makes sense when you realize the GJ is tapered pretty evenly, and as the airflow increased, the needle allowed a significantly increased rate of fuel, but not the gobs more offered by the LS1, 7 and RO. The GJ were highly successful in the XPEG and XPAG TDC for that reason (the LS1 being way to rich for the XPAG TDC as originally spec'd).

The trick with SU carburetors is staying in the 80% airflow capable area, and certainly not exceeding about 85%. After that the venturi effect at the bridge is reduced because of the low height of the bridge and the lack of an upper piston indent to speed up the flow properly compared to the initial inlet.

Hope this helps,
dave
Dave Braun

Hi Dave

You rebuilt those carbs for me. Would you recommend the GJ at my altitude of 7000' for a 1.5 carb on the supercharger.

Funny it seems that every time I read about a supercharger application the first warning is to make sure it does not run lean throughout the entire power ban. Seems richer is OK. Second warning is run high test/ premium gas.

Joe
JWP Policastro

Richard thanks for the articles. Both kind of highlighted having manageable and specific goals.

Seems my plan of three sets of Dyno days was a reasonable one. For those who do not know. This was my plan.

Do a day with my stock car to see what the base line was. This included installing new points, plugs, timing, etc. in other words a complete tuneup prior.

I was then going to return home and remove my head and install my spare rebuilt head which was done to MGC specs with larger valves that had been polished etc. and has a totally rebuilt rocker assembly. That head is running about 8.3 compression.I was going to return to the Dyno and see what the difference if any was.

The third day on the Dyno was after some further mods. I am going to install one of Tom's superchargers and install a rebuilt distributor that was set up for a supercharger. I was going to keep the modified head used on day two on the Dyno.

This procedure will hopefully will allow me to see the differences between a stock system, the value of a modified head and lastly what the supercharger and correct distributor setup was adding to the mix.

Tom suggested testing different levels of plugs. I run a stock oil bath filter which will be gone when the supercharger is installed.

The cost will run these tests is about $240 for the three trips to the Dyno.. As you can see you have limited time in a hour to make major adjustments.

Joe
JWP Policastro

You are going to have a .100 jet in your blower carb Joe and not a .090 for starters. With the blower you would ideally be a little rich on full throttle application yet seeking a normal A/F mix during any other run. I'd suggest you take some 90 wgt gear oil for the damper as this will give a richer mix on full throttle. You might also want to have some automatic transmission fluid in case you find that it does a total over rich bog off the line to get the opposite effect. You could do the same thing with some different damper springs if you have them. Have the dyno operator send you a pdf of the runs individually and then overlayed so you will have them to compare...and also it would be great to see them here.
MG LaVerne

Thanks LaVerne.

This will not be a quick process. There is a delay on one of the parts for supercharger. Expected to arrive in May. Tom has been great just a production issue that he has no real control over. I have been on the other end of those so I understand.

I thought it would be better to post the results all at one time but maybe the first two runs makes more sense then followed by the entire set.

Hopefully the last snow is falling as I write this so the first run should be done in about two weeks. I need to move the TD to the lower heated garage to work on the head. Daytime temps are still a little brisk and we are still below freezing at night. So the second run will happen hopefully in about two weeks after the first.

The reason for the Dyno runs is really not so much for me but to provide some actual, real empherical data for things that just get said and never proven, disproven or ever validated.

So yes I will post when done with at least the first two runs with the stock carbs followed by all three in a package.

If you want a hard copy email me the address and when I get it I will send you a set.

Us high altitude guys need to stick together. Best number is we lose about 25% of our power and boost drops from 6.0 to about 4.5 up here.

Joe
JWP Policastro

Yes I'd like to see the results. You are waiting for the choke cable bracket?


You shouldn't lose that much boost but you will lose a lot of hp verses sea level for sure.

MG LaVerne

Joe,

Sorry to be late. With an H4 and a .100 jet, I would start with RA and see how far I had to lean it to get reliable running. Make sure the float is set at or slighty deeper than 7/16 of an inch. Look for fuel to be about .18 below the jet... really hard to measure but with patience you can baseline it.

Then I would bring along a GK for lean and try that. It might be too lean. Finally, the KW starts leaner, so it can be enriched right away, and ends richer, if you are having lean firing at speed.

From there I would get out a piece of emery paper and remove material, measure later, and find the closest comparable needle. To be truthful, in the short fixed needle style, the RA is about as rich as it gets. When you are running at different throttle and loads, note the height of the piston (a small camera is handy) and you can figure out where you may need to adjust your fuel.

Warmly,
dave
Dave Braun

The RA needle is the one I provide with my supercharger kit, which Joe is buying.

Flagstaff is about 7,000' in altitude.

Tom Lange
MGT Repair
t lange

That's reassuring, Tom!

Warmly,
dave
Dave Braun

I'm going to be talking with Joe Curto next week, and plan to ask him which needle he recommends for that altitude.

Tom Lange
MGT Repair
t lange

This thread was discussed between 30/03/2016 and 02/04/2016

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