Air Filters and Engine Performance

[Leeds Sprint]

Thanks for that Martin, Julian and all the rest.<br>
<br>
That sounds like good advice. I have a few other things that need investing in first. New suspension is a priority for the Dutchess! She handles a bit rubbish right now. After that though, Ill be looking to do something with the exhaust. <br>
<br>
My 1850 is my everyday car, so getting it running smoothly has been a priority for me. I have fitted a lumnetronic ignition which has been the most recent step taken in this regard. It does seem to be running well.<br>
<br>
I am very curious to know what the performance of my Dolomite is now, and what it would be if I made some improvements to induction and exhaust. It seems that a rolling road is the best to find out, but it does seem quite expensive. <br>
<br>
Is it essential to use a rolling road to tune my carbs? Could I not just make the improvements to the car and then just get the carbs tuned by a qualified garage? I understand that it will be hard to identify how much of an improvement I have made, but I'm not sure if I can afford £80/hour on a rolling road. <br>
<br>
Thanks<br>
<br>
Chris<br>
<br>
Thanks<br>
<br>
Chris

<p></p><i>Edited by: <A HREF=http://p206.ezboard.com/bthetriumphdolo ... ckinson</A> at: 16/8/06 2:40 pm<br></i>

[dollysteve]

Not essential but a good idea. The RR operator will also put a gas analyzer up the exhaust, this will allow the mixture throughout the rev range to be monitored, they will therefore be able to try different needles until the they get the desired results, this will obviously mean taking it to someone who has experience of SU`s and a good stock of needles, the only place I know of with a RR, good stock of needles and the knowledge is southern carburettors in wimbledon. I`m sure some other people on here know other places though.

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[davepoth]

The thing is the car as it is is probably nowhere it's potential with the standard components. Getting the timing and fuelling correct may make quite a big difference to the car. You don't really need a rolling road for SUs, just find a good garage which employs a mechanic near to retirement age and he should be able to get your car running nice. But I'd definitely recommend getting the setup done first, just to get a good baseline before you spend £200 on a new exhaust and fancy air filters.

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[Jon Tilson]

An SU is only adjustable mixture wise at idle really and off load. The needle profile was chosen by the makers to then give a reasonable mixture profile throughout the rev range. You can make a change of needle and/or a change of Spring to alter the air valve characteristics too. I tend to never change the spring...perhaps I should. Chances are your needle is right for the standard setup. One way of telling if a richer one would help is to cruise at say 60 ish and pull the choke out a little so the jet drops. If the car suddenly feels livelier then you are running weak higher up.<br>
Your car should also pull 70 in 3rd and feel lively in the process...if pulling the choke makes it go noticably quicker again its weak at the top end.<br>
<br>
Jonners

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[2F45T4U]

So what difference does the spring make? I've got needles matched to my air filters and exhaust according to Triumph Tune manual but changed the springs to shorter ones. <br>
<br>
If I tried longer ones what can I expect?

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[george]

if zebedee had a longer spring how far would he go<br>
bouncing along ???

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[2F45T4U]

So I'd bounce further?

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[Leeds Sprint]

My 1850 has a non-overdrive gearbox. It revs to 4000 rpm in 4th gear. What would the engine speed be at in 3rd gear? Frankly, I'm not sure I'm brave enought to do that.<br>
<br>
What sort of sustained engine speeds are safe in a Dolomite 1850?<br>
<br>
thanks<br>
<br>
Chris<br>
<br>


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[davepoth]

4500-5000 should be absolutely fine all day long if the engine is in good condition. 65mph is maximum for 3rd gear, so I wouldn't recommend it.<br>
<br>
-edit- <br>
<br>
And of course reading Jonner's reply below, 65 is the maximum for 2nd. Really should stop replying to things before I have drunk some tea. <!--EZCODE EMOTICON START :o --><img src=http://www.ezboard.com/images/emoticons/embarassed.gif ALT=":o"><!--EZCODE EMOTICON END-->

<p></p><i>Edited by: <A HREF=http://p206.ezboard.com/bthetriumphdolo ... avepoth</A> at: 17/8/06 9:47 am<br></i>

[Jon Tilson]

A dolly 1850 is geared at about 19 per 1000 in top so 4k is about 76 mph. If the speedo reads roughly this you are near enough..<br>
A dolly will do 90 in 3rd but its a bit pointless. It should do 50-70 in 3rd a good bit quicker than it does in top.<br>
If it doesnt, try pulling the choke as you accelerate..<br>
If it picks up better then you could use richer needles.<br>
Jonners

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[Leeds Sprint]

Okay so I have made it to work having successfully implemented Jon's fuel mixture test.<br>
<br>
At 65 mph in 3rd gear (didn't quite have the guts to go to 70) I pulled my choke out and looked for any performance changes with various ammounts of choke. I didn't notice any difference.<br>
<br>
At 85 mph in 4th gear I tried the same. Again, there was no real perceptable change in performance or smoothness of engine running. <br>
<br>
So, if I have understood the test correctly.... with no change in performance with the choke being used at high speeds, it can be concluded that the carbs are set up properly for high revs. <br>
<br>
It's worth pointing out that the car doesn't need to have much choke when starting up, and very soon benefits from it being pushed all the way in (less than a mile usually).<br>
<br>
Is that right Jon? Is it fair to assume that the garage that tuned my carbs following the installation of my electronic ignition must have done it properly? And that the performance I am experiencing is an indication of what I can expect using standard equipment (exhaust and induction) fitted to 1850s)<br>
<br>
Thanks<br>
<br>
Chris

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[davepoth]

One thing that might be worth checking is making sure the distributor is advancing properly throughout the rev range.

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[Jon Tilson]

if you can see an easy 85 in 4th there isnt much wrong with it really...<br>
Did it seem to have more left?<br>
My clone of yours (R plate tahiti 1850 with o/d) has had a waxstat conversion by the p/o and it is flat above 80 but goes when the choke is pulled.<br>
<br>
May be worth checking the advance works with a timing light but what happens with the delco dizzy is the springs go weak and it advances too quickly...so I doubt it will make much difference.<br>
<br>
What mpg do you get? I find its hard to get a good 1850 below 30 mpg..<br>
<br>
Jonners

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[Leeds Sprint]

Jon<br>
<br>
In 4th gear at 85mph on the flat, there is some spare umph. It seems to be pulling quite strongly.<br>
<br>
I do seem to be getting pretty good MPG as well. I managed just under 35mpg earlier this summer. That was an average over a whole tank of petrol at mostly motorway miles.<br>
<br>
<!--EZCODE QUOTE START--><blockquote><strong><em>Quote:</em></strong><hr>My clone of yours (R plate tahiti 1850 with o/d) has had a waxstat conversion by the p/o and it is flat above 80 but goes when the choke is pulled.<hr></blockquote><!--EZCODE QUOTE END--><br>
<br>
What does p/o mean. And what is a waxstat Can't figure that one out. Sorry im a bit new to all of this.<br>
<br>
Thanks<br>
<br>
Chris

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[davepoth]

P/O-Previous owner<br>
Waxstat carbs were the later type of carb which were fitted with a jet that adjusts the mixture when the wax in the jet warms up, ofr some emissions or economy related reason. <br>
<br>
When they get old, they tend not to work properly and then the mixture gets messed up, so many people remove them and fit solid jets.

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