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Hi All. After 16 years of ownership I sold my Tr4a two weeks ago but I still have many happy memories to cherish. Two days ago I purchased a tr7 in nice condition and really basic i.e. No mods . I would like to get a few more Bhp out of the standard motor and was thinking k and n air filters  4 into 2  extractor  manifold electric fan   . Is this the way to go and is there anything else I am not looking for a race car just a good continental tourer . Thanks 

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I found the extractor manifold didn't make much difference. However, what did was a good straight through stainless steel exhaust system. Either the sports or standard boxes. Most standard boxes are now straight through. If in doubt get the sports system. On the carbs side fit K&N's with BDC or BAE needles. BAE are slightly richer and overall give a better performance.  I have tried the recommended BAL needles with, and without the full sports exhaust system and found them too rich. Also small rams inside the K&N's help. You don't have to change the carb piston springs.

The above gives good low end and mid range torque, plus free reving at the top end. It wakes the engine up. I find the better torque makes the difference when driving long distance.  These mods have been carried out on three TR7's and all gave the above results.

Dave

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Thanks DaveR.  What about swapping points for electronic any plusses there and removing mechanical fan replacing with electric 

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Yes electronic ignition will give a small power gain. It also gives better starting and smoother running. Plus of course the points are a pig to get to. 

There is loads of room to fit an electric fan. The power advantage would be very small, but it's still worth doing as it will give a quicker warm up.

Dave 

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37 minutes ago, DaveR said:

Yes electronic ignition will give a small power gain.

Unfortunately that is not true for an otherwise unchanged ignition system, though the other advantages may be.  The spark energy depends solely on the magnetic energy stored in the coil. How that is switched - whether with a mechanical contact or with a transistor - makes no difference at all to the spark, so there can be no power increase over a properly adjusted un-worn points system. 

 

 

Edited by RobH
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It depends on your perspective, but on the basis of my Grinnall, a V8 conversion has a lot to offer. 

Whatever you choose, I hope it all goes well.

 

Edited by acaie
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23 hours ago, RobH said:

Unfortunately that is not true for an otherwise unchanged ignition system, though the other advantages may be.  The spark energy depends solely on the magnetic energy stored in the coil. How that is switched - whether with a mechanical contact or with a transistor - makes no difference at all to the spark, so there can be no power increase over a properly adjusted un-worn points system. 

 

 

RobH, Agreed that is the theory but in practise there is a small power gain due to the limitations of the mechanical  points switching arrangement. A lot has to do with the high current being switched through the points.

Dave

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49 minutes ago, DaveR said:

in practise there is a small power gain due to the limitations of the mechanical  points switching arrangement

Sorry Dave but there just isn't -  it is a myth.  Points are actually a less lossy switching mechanism than a transistor, whatever the makers of the electronic systems may say in their advertising .  

The current being passed is not high - with a 3 Ohm coil it is 4 amps or so and points will pass that with zero voltage drop. A transistor switch always exhibits some low resistance even when fully 'on' and the saturation voltage may be some tens to hundreds of millivolts. In theory then the transistor switch is ever so slightly worse though it makes no practical difference to the spark. 

What usually happens is that people fit electronic ignition to an old and worn distributor. The new system makes up a little for some of the wear and this is interpreted as 'more power' whereas all it really does is get back to where things should be with a standard un-worn system.

It is possible that better overall performance results from using one of the wholly electronic distributors like the 123. This is not due to the elimination of points but rather to being able to select an advance curve which better suits modern petrol.  The result may be better low-speed pickup though the rev range but even with these the power peak will be the same as for a conventional distributor, because the maximum advance for the engine cannot be exceeded.  A standard points distributor with that same advance curve would give exactly the same performance gain.

 

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4 hours ago, RobH said:

Sorry Dave but there just isn't -  it is a myth.  Points are actually a less lossy switching mechanism than a transistor, whatever the makers of the electronic systems may say in their advertising .  

The current being passed is not high - with a 3 Ohm coil it is 4 amps or so and points will pass that with zero voltage drop. A transistor switch always exhibits some low resistance even when fully 'on' and the saturation voltage may be some tens to hundreds of millivolts. In theory then the transistor switch is ever so slightly worse though it makes no practical difference to the spark. 

What usually happens is that people fit electronic ignition to an old and worn distributor. The new system makes up a little for some of the wear and this is interpreted as 'more power' whereas all it really does is get back to where things should be with a standard un-worn system.

It is possible that better overall performance results from using one of the wholly electronic distributors like the 123. This is not due to the elimination of points but rather to being able to select an advance curve which better suits modern petrol.  The result may be better low-speed pickup though the rev range but even with these the power peak will be the same as for a conventional distributor, because the maximum advance for the engine cannot be exceeded.  A standard points distributor with that same advance curve would give exactly the same performance gain.

 

Which is another reason to send your distributor to Martin http://www.distributordoctor.com/  For a full rebuild.

Stuart.

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RobH, I agree that many an electronic ignition has been used to try to overcome the problems with a worn the distributor. However, the 4 amps through the points does create limitations,  even amplified systems that retain the points give better results due to the lower current. That is providing there is still sufficient wetting current present to keep the points clean, 500mA is about right.

Also there is point bounce to consider at high RPM when comparing both set-ups

When designed correctly electronic switching is cleaner and more predictable.  The advance curves are a separate issued.

I guess we agree to differ.

Dave

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