Timing and tuning

[grumpy2]

Further investigations have been carried out.

 

I have a relay fed fuel pump. The relay is under the bonnet and is fused. It feeds the existing white rule pump wire from under the bonnet.

 

I think a better solution would be to relocate the relay near to the fuel pump and feed the pump by a dedicated circuit directly from the battery but switched via the relay. Does this make sense? I can use the existing White wire to energise the relay in the boot.

 

Am I on the right lines?

[Ade_TR6]

Spot on... Exactly how i did it. The existing white cable is a little undersized and has a big voltage drop across it hence little difference with a relay under the bonnet...

[barkerwilliams]

Whilst running a new power cable to the fuel pump don't forget the return circuit via the earth. If the earth is poor it does not matter how good the supply cable is.

 

Alan

[grumpy2]

Rewired direct from battery and new earth via fuse and relay

 

Showing approx 0.6v drop under all conditions so a significant improvement. May be my imagination but pump certainly sound higher pitched so pumping more

 

No road test yet. Tomorrow probably.

 

Gary

Edited August 17, 2015 by grumpy2

[John390]

Well? We are all waiting for your vast improvement results!

 

 

Cheers John

[grumpy2]

Sadly the lure of taking my old mum for an ice cream in Blackpool proved too great. 200 mile round trip for a 99 in the freezing wind! Hopefully tomorrow if it stays dry.

 

Sorry

[grumpy2]

Well well. Started first flick this morning from cold. A bit lumpy but decimate improvement. Hot starting too much better not first flick but only about 3 seconds cranking. Fluke or genuine improvement? Who knows the rainy season has started as I write.

 

Gary

[peejay4A]

Good news. What about your fuel pressure? You might be able to get it even better or at least have the peace of mind that it's right.

[grumpy2]

Trying to think of an easy way to measure it. Seen some post about folk who've fitted in line pressure gauge points for £60-70. Taking it to TR Bitz is a treck and would only get measured once for the same cost. I'd rather have a system I can use myself and monitor as and when I wanted

 

Car seems to pull a little better too, but this could be the rotor arm, coil, changed timing or fuel pressure. Or may even be just my imagination.

[Kevo_6]

Trying to think of an easy way to measure it. Seen some post about folk who've fitted in line pressure gauge points for £60-70. Taking it to TR Bitz is a treck and would only get measured once for the same cost. I'd rather have a system I can use myself and monitor as and when I wanted

 

Car seems to pull a little better too, but this could be the rotor arm, coil, changed timing or fuel pressure. Or may even be just my imagination.

Hi Gary

 

I have that set up, got to take my gearbox out tonight but give me a few days and I will get you some part numbers.

[barkerwilliams]

I used one of these @ £12.61. Needs a T piece to the prv, or the MU. As the gauge is electronic with a sender unit no fuel flowing around the car to the gauge.. Just a single wire to the gauge.

 

Probably not the best to leave installed permanently but can be used for a couple of days until you are happy with the readings from hot / cold starts etc then removed.

 

 

 

Alan

[grumpy2]

Kevo, that would be perfect.

 

Alan, one of what??

[barkerwilliams]

Arrrrghhhh!!!

 

http://www.ebay.co.uk/itm/UNIVERSAL-2-52mm-PSI-BLACK-DIGITAL-LED-OIL-PRESSURE-PRESS-GAUGE-Meter-CAR-UK-/291035804701?hash=item43c315f41d

 

CTRL V to paste link didn't work.

 

 

Alan​

​

[grumpy2]

pooh what sort of T piece did you use?

[jojim65]

Grumpy,

 

You need the following from Hydrotechnik,

 

http://www.hydrotechnik.co.uk

 

9807-160 for 63mm Pressure Gauge up to 160psi with rear entry,
SNA02 for the Test Tee Piece with 1620 Test Point fitted,
S103-AC-FA-00.80 for the 80cm connecting pipe with sprung support at each end.

 

Plenty of us on here have bought these items and they work a treat, chose a longer hose if you want to read the gauge in the car whilst testing.

 

Jim

[Kevo_6]

Grumpy,

 

You need the following from Hydrotechnik,

 

http://www.hydrotechnik.co.uk

 

9807-160 for 63mm Pressure Gauge up to 160psi with rear entry,SNA02 for the Test Tee Piece with 1620 Test Point fitted,S103-AC-FA-00.80 for the 80cm connecting pipe with sprung support at each end.

 

Plenty of us on here have bought these items and they work a treat, chose a longer hose if you want to read the gauge in the car whilst testing.

 

Jim

 

Thanks Jim, saved me looking it up.

[RobinTR6]

Kev, I've got the hydrotechnic setup, works great. As advised get plenty of hose so you can view in car whilst driving, my pressure dropped significantly only when cat being driven so worth the extra few pounds, good luck.

[Peter Cobbold]

Kev, I've got the hydrotechnic setup, works great. As advised get plenty of hose so you can view in car whilst driving, my pressure dropped significantly only when cat being driven so worth the extra few pounds, good luck.

Robin,

That's interesting. I wonder if all PIs do that when correctly set up? Nothing like measurements when tuning.

Peter

 

May I make a general observation. Checking the fuel pressure with the car standing still will not test whether it is correct at full chat on the road.

When tested in the garage an engine at tickover uses maybe a couple of horsepower, and not much more revving at 5000rpm, just enough to overcome internal friction and drive ancillaries: very roughly 5hp at 5000rpm. That is 30-fold less than the 150hp engine at 5500rpm wide open throttle on the road. The point is, the flow of fuel follows horsepower, so fuelling also has to rise when the engine is loaded: up to 30 times more fuel flow than the static test involves.

So if we follow the fuel system form tank to injectors we can see that anytihng that limits the faster flows needed in a loaded engine may not be apparent on the driveway test, including:

Inadequate size of fuel filter, or clogged filter, too small capacity pump, or pump that leaks back to its input, PRV dumping too much flow ( psi set wrong) or unable to pass enough flow ( psi at MU higher at tickover than when running loaded).

So by considering flow we can see that a weak pump can easily deliver the correct 106psi at tickover but less pressure under load. And it could appear to be weak because the filter is incorrect.

What is needed I think is a way to monitor fuel flow, while driving, up the return hose to the tank from the PRV. If the filter pump etc are OK then the PRV should pass a huge flow at tickover and 30 fold less at full chat. Maybe something like this:

http://www.race-technology.com/fuel_flow_sensor_2_728.html

Edited August 20, 2015 by Peter Cobbold

[Steves_TR6]

I like your thinking Peter!

 

So we need a means of measuring pressure at the mu, and pro flow back to the tank for a complete solution.

 

I'm suspecting one reading would be proportional to the other !

 

Steve

[Tim D.]

I think that the more important problem with doing the test out of gear is that somehow you need to maintain 5500 rpm with the throttle fully open for enough time for the pressure in the fuel lines to equilibrate. Maybe possible on the road where the load reduces the speed at which the engine accelerates.. Impossible with no load as the engine would quickly exceed redline. Unless of course you have a Rev limiter.. Then it would work as the MU is "dumb" and will only see the atmospheric pressure reading from the wide open throttles and the 2750 rpm (half crank rpm) from the cam shaft..

Or am I misunderstanding.

Tim

[Peter Cobbold]

I like your thinking Peter!

 

So we need a means of measuring pressure at the mu, and pro flow back to the tank for a complete solution.

 

I'm suspecting one reading would be proportional to the other !

 

Steve

Steve,

The unknown complcation is how much fuel a pump pumpng into 105psi normally leaks back inside itself. If it leaks a lot back wards when flow at the MU is slow ( ie low loads) , but leaks less when the engine is working really hard ( fast fuel flow) it is itself acting rather like a PRV. So the PRV flow may not be found to be strictly inversely related to horsepower.

What a consideration of flows does suggest is that a 'pick and mix' approach to changing pump or prv may end up with an imbalance in flow capacities.

Peter

[Peter Cobbold]

I think that the more important problem with doing the test out of gear is that somehow you need to maintain 5500 rpm with the throttle fully open for enough time for the pressure in the fuel lines to equilibrate. Maybe possible on the road where the load reduces the speed at which the engine accelerates.. Impossible with no load as the engine would quickly exceed redline. Unless of course you have a Rev limiter.. Then it would work as the MU is "dumb" and will only see the atmospheric pressure reading from the wide open throttles and the 2750 rpm (half crank rpm) from the cam shaft..

Or am I misunderstanding.

Tim

Tim

Impossible ! - full throttle out of gear...bang !!! At wot and 5500prm the engine could produce 150hp but only needs 5hp to spin it...revs will go skyhigh. A rev limiter will kill the spark until most of the fuel is wasted, unburned.- and that of course kills most of the horsepower.

 

To me, load ( ie horsepower) comes first, then that determines fuel flow. Rpm I regard as secondary, because we can have the same horsepower at say 1000rpm wide open throttle as at part-throttle cruise eg 2500rpm,50mph ( at a guess about 20 hp). The optimum AFRs for wot and for cruise then comes as the third considerationand that's where the MU depression and cam come into play.

 

In short, the psi test out of gear cant replicate any but the smallest horsepowers. Hence the fuel flow tested will be a small fraction of that need at full chat.

 

Peter

Edited August 20, 2015 by Peter Cobbold

[Tom Fremont]

^{I don't see how the factory static timing setting can be reconciled with lower octane fuels. Even the TR250 manual specified 100 ( Research method ) octane which is higher than anything available over here for decades now.}

 

^{On Webers my otherwise CP engine can't do with more than 10 deg BTDC static without some pinging in the mid range ( not sure I'd hear it beyond ). Distributor is 41219, btw. Fuel is alcohol laced 93 octane (R+M)/2 , ~ = 97 R}

 

^{And the AC mechanical fuel pump supplied on all Federal cars keeps up with the triple DCOEs just fine.}

 

^Cheers,

^Tom

[Peter Cobbold]

Hi Tom,

Now there's a puzzle...

With 9.5:1 compression I dont know why the factory specified 100RON. Unless it was to avoid any risk of warranty claims from driving in the hottest, driest, possible driving conditions that would ever be encountered in USA - eg Death Valley. The 250 was only sold to USA....

 

How much ethanol is in your fuel?

If the base fuel is 93RON gasoline it needs 15% eth by volume to bring it up to 97RON:

( Ford data):

https://supertrarged.files.wordpress.com/2013/08/ethanols-impact-on-ron-octane-ratings-in-gasoline-ford-data.jpg?w=450&h=395

I dont have (R+M)/2 figures.

 

The ethanol will lean the mixture unless the carb is richened to compensate. As eth has only 65 % of the heating value of gasoline, 15% eth will be leaner than 15% gasoline by 65% of 15 = 10%, leaving a mixture deficit of 5%. If the jetting is not increased the ethanol-doped fuel will run at about 0.75 AFR lean from the pure gasoline AFR. eg if gasoline AFR were 13 then eth-gas will give about 13.75 ........That's not a lot of difference, I cant see it making it pink at constant full throttle.

 

If the pinking is transient after flooring the throttle I'd supect the reason is that ethanol is slow to evaporate in the intake manifolds. Ethanol is very much less volatile than most components of petrol. The fraction that the engine sees intially after wot will be deficient in ethanol and the RON of the inducted mixture will be low.

The same thing happens with petrol in the PI set up where there is no acceleration enrichment. The less volatile component of petrol linger and wet the manifold walls, but these are are needed for the high octane. Result: the engine first takes in a fraction of more volatile but low octane hydrocarbons. Pink, pink, pink.

 

cheers

Peter

Edited August 20, 2015 by Peter Cobbold

[Tom Fremont]

Hi Peter,

 

Actually, TR250s had 8.5:1 c/r. I wondered why too, but then you do get more power and fuel economy from higher octane fuels ( if not much ), right? Anyway, I don't know the octane rating's influence from the ethanol.

 

Alcohol content is not more than 10%, but could be less. Its presence causes some difficulties in hot idling situations where carb bowls sitting over exhaust manifolds start boiling it a little. Otherwise I can't find any issues beyond feeling the need to put additives in to compensate for rapid fuel degradation / aging etc. Old fuel pump diaphragms can't take the alcohol but the current ones can.

 

Cheers,

Tom