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Triumph TR6 - Dyno&tuning session

Sorry I'm bombing the board with posts, but I thought I'll start a different one as this is a complete different matter...

I've booked a tuning session at a reputable rally car builder/tuner, hes got a rolling road and a "distributor bench", and I am basically interested in finding the right needles for my twin HS6, and in getting the distributor advance curve right for my application.

Question 1: Should I prepare the car in any particular way? The engine was rebuilt during the winter, its been broken in & serviced during this summer, so everything should be ok. But are there any particular things to look out for or check?

Question 2: I have fitted an early PI head, slightly polished and port matched, twin HS6, SS extractor & pipe, road 83 cam and changed the points to a Newtronic system. According to moss europe's catalogue this could give me an extra 35-40 bhp over stock. What do you think, are these kind of figures realistic? It sure does not feel like 145 bhp at the moment, but when (if??) I get the dizzy&SU's set up right?

Question 3: Are there any gains to be found in tweaking eith the cam timing? Do any of you have experience with this?

Looking forward to your comments & I will be reporting the results whin this is done!



the more posts - the better!

1) Be sure to bring all your tools so you can get the most out of your session.

2) I hate it when outfits make HP estimates - people always get hopeful and then face a let down. You should be interested in torque and where it is in your power band.

3) Cam timing allows one to adjust where the power comes on. You can move the power band up or down by changing it. The chassis dyno people should give you a good idea where to move it and if you should.

Have fun!

Tim Brand

I have done this several times with my TR4a, and it is very interesting; certainly separates facts from opinions!

1) A dyno run is over reasonably quickly since there is no wind resistance to slow down your acceleration, so the procedure is likely less stressful than a top speed run on the road (if you could do such a thing legally and safely), just change the oil and make sure your coolant is good. The dyno shop will cool the car with a big fan, and will allow 10 mins or so between runs. If your oil is very full you may lose a bit, set it just below the mark.

2)Results may vary... I would guess the combined effect of these changes would be less, perhaps 20-25%, but you don't mention compression ratio, which is very important, especially to get the biggest gain from the cam. If you can, get a friend with a stock TR6 to test his/her car as well so you have a baseline. Some dyno shops save the info on a disc drive and may have done a TR6 in the past so can reprint it for comparison.
The SU carbs instead of Strombergs, and the electronic ignition may provide very small gains but are better for other reasons.
See if you can pay extra to get drivetrain losses measured, this will allow you to calculate power at the crank from your rear wheel figure. My guess is a stock North American TR6 should make around 85bhp. at the wheels, and about 110-115 ft.lbs. torque. Please let us know your results!

3) Sorry to be so long winded in my response. You can only change cam timing on initial installation of the cam, or by means of vernier cam pulleys.As Tim correctly states you can fine tune the shape of the curve slightly by doing this but its more a consideration for outright race engines, so don't worry about this. Getting mixture and advance curve dialled in will give a bigger gain for less effort. This is where you want to concentrate.

I am planning to write an article on this subject for our club magazine so would love to hear from you afterwards!
Simon Rasmussen

Since it wasn't mentioned SR I have to throw in my .02.

Timing, valve lash, clean fuel filter, clean air filters, and MAKE SURE THE THROTTLES are opening FULLY!

Don't ask me how I know about the last item.

Jim Deatsch

I would get the distributor set up on the bench first - getting it close to the specs you want. If you are changing springs to change the advance curve characteristics, have say two or three combinations bagged and ready to change over between runs. To do it on the dyno could be expensive if you are starting from scratch with the dizzy.

Most important with the dyno is that the readout is "SAE corrected" as results will vary between machines. The "corrected" figure will get the computer to correct for air temperature and barometric pressure. [SAE: American standard. Measure at 99kPa and 25C. Rated in hp. 1kW = 1.341hp (SAE).] These are taken as separate readings immediately prior to the test and entered into the system manually. It is the only way to have a direct comparison with other vehicles, but more importantly to be able to compare changes to your own car on different days. There should also be a memory facility where your info can be stored and recalled later. You can then overlay different runs to get the comparisons.

In addition, you may also be able to get an exhaust gas analysis done at the same time to help you get the mixture right. The mods you have done will probably need more juice to show the benefit.

The rear wheel horse power will be approx 18% less than the engine HP (which is measured at the flywheel). Also losses for cooling fan, alternator, power steering etc etc are often not taken in to account when manufacturer's quote power output figures.

I had a quick run on one just before going overseas and it ended in a mess!!The electric cooling fan relay chose a bad time to go south! Giving it stick while stationary soon had a fountain of coolant out of the overflow bottle. If not for that, I would have been posting some comparative results (which will now happen in a few weeks as the (PI) metering unit is interstate for re-calibration)

Don't expect too much and you won't be dissappointed (and make sure you have enough gas in the tank to get you home!!)

Good luck.
Roger H

I think an update is in place here...

Yesterday I started experiencing a quite noticable clak-clak-clak (increasing with speed) from the rear when engine&drivetrain was under load.... I was really annoyed, I haw brand new U-joints, I've had the hubs checked. Anyhow a scary sound and left rear wheel leaning in means that there will be no dyno&tuning session on friday and monday as planned. I will schedule a new time a soon as the car is on the road again...

Thanks for your comments! A few comments: I'm not really that interested in getting an accurate hp measurement, I am more conserned about getting the engine set-up right. What we had planned with the shop was: 1. check that the dizzy is working properly 2. Find a couple of spring combinations to try on the dyno 3. Dyno runs with the objective to find most suitable spring combination for the dizzy, and check the exhaust to get a picture of how well suited my current needles are. The shop does not carry a very large needle selection for the HS6, so that probably means I will have to buy (or perhaps borrow??) different needles and come back again.

Thats basically wht I want to do, and what I will do as soon as...

The engine was as I mentioned rebuilt last winter, and it has been serviced and checke after I considered it broken in (oil, valves, timing, carbs etc), so I think it should be ready for this.

I will get back and post results as soon I have somthing to report...


This thread was discussed between 10/08/2004 and 12/08/2004

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