Tag Archives: Dyno

Dissapointing dyno result – Solved..!

This few days, I can not sleep and eat.. I wish I did not do the Dyno.. :). But that is the beauty of having old car, this problem is actually a lot more interesting than problem in the office, you do not know what is wrong… it just does not work as expected but the good thing is almost everything under our control to solve it…

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Dolly at Dyno machine

So what is wrong then… if you read my previous post, you know that Dolly power is low, and peaked at 3000RPM, which should be around 4500 RPM and  lot higher.  A lot of things can be the cause, I need to check it one by one…

  1. Engine Compression, may be the compression is low and resulting low HP… checked… and the result is 165 psi across all pots. so no problem here.
  2. Fuel supply problem… how can it be..? I just replace the seal… and seems works ok
  3. What about ignition timing..? I checked using strobe and the result is 5 deg, should be no problem…
  4. The suspect  now is the carburetor SU HS6 or electronic Ignition or problem with the timing chain

The fellow land rover forum said that the Electronic Ignition can be faulty, or since I do not know the advance curve of this distributor, it may be not suitable for landrover… to prove this point, I did an exercise… set the ignition timing too advance (deliberately) and drive it full power (stopped when it start knocking), and then retard it a bit and drive it full power again, and so on and so forth until the timing is too retarded  loss power at all RPM). In this exercise, I found that no matter what, I lost power after around 3000 RPM at all ignition timing set up. So the Electronic ignition is no longer suspect.

Now how about carburetor, again little exercise in the morning, I set the jetting from too rich to too lean, again the result is the same.. loss power at around 3000 RPM. and I gave up… I am not bother checking the timing chain, the symptom is not relevant for timing chain. I just use it at low rpm, but back in my mind I always have that question… “what the hell is wrong”  something is fundamentally wrong and we can not find out what it is..? even my fellow land rover forum who usually very knowledgeable on this matter can not solve this riddle.

Finally I went to local Land rover garage and discuss it with the garage owner, I show the dyno result… just with one glance he said… ” Fuel supply problem..!”. Can not be… I replaced the seal and clean it… “Fuel supply problem..!” he said again… How can it be..? I challenge him… “FUEL SUPPLY PROBLEM.. ! DAMNED..!” he almost throw the “land rover number one tool” at me.

Ok Ok.. I said… how to solve it…? He then installed an electronic fuel pump after the mechanical lift pump… “this will do” he said. “let me know how it goes…” Why not install it before the mechanical pump..? me questioning his installation… “you fool..! you want the fuel flood your engine and blow you up…?” and it shut me down… :) here is the installation..

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Very true.. this solve the problem… I can feel Dolly is still pulling even after 3000 RPM, very happy, I say thank you to him (and pay of course) and drove home smiling… I do not bother to dyno it again… one because I have to pay, two I am afraid that I will find another problem that keep me awake during the night… may be later, but not now :)

So moral of the story is… don’t dyno even if it is free…. ah ha ha..

Dissapointing Dyno (rolling road) Result…

Last weekend I got a good offer from a garage owner friend who wants to dyno Dolly, I think he is a bit curious about dolly. Of course I agree,  it is always good to know the power curve of our car.

I am very confident that Dolly will get a good result as I already upgrade few things : Electronic ignition and Carburetor  and I have rebuild the engine.  so the expectation is : I will get higher power than stock, there is no way it will be lower. Finally the day came and we prepare Dolly on the rolling road, setting up big  fan in front of Dolly  to cool her engine.

Full of expectation, my eyes set on the computer while the operator revving the engine as high as he can…. A lot of gibberish number, I only want to see one thing… 70 or above… that is the HP (horse power) for stock engine… however that number never came… and when I see the operator is amused (not in a good way like scratching his head), my heart sunk… oh my God… whats wrong…?

And then he asked the owner to try to operate dolly.  He too also gives a “give-up” look and then he ask… what is the engine cc..? “2.250 cc” I said and hastily added “low RPM torque type of engine” to make sure he understand that peak torque is around  2200 RPM not like racing cars.

Do you know the peak BHP for this car… “at least 70..!”  Me answering his question…  “Yeah I thought so” he said… fiuh… I feel relieved…  so all the confused look is seems because they expect a gazillion torque or horse power  like many of their racing customer cars. ” So what’s the result look like…” I impatiently asked.

“Not even 50 BHP” … hearing him saying that, you will feel like you got stung by hornet in the forehead… he see me stunned he continue his sentence:  “yap… we have tried it three time and the result is the same… sorry…”  and then he gave me a print out showing the result.  To give you a perspective on the dyno result, here I charted dolly BHP and added “Standard” engine BHP from their brochure (I actually stole it from Darren one of the land rover forum friend).

BHP dolly
The standard engine BHP is measuring the engine on the flywheel (engine Power) while dolly is using on the wheel (wheel power), so the gap is acceptable, sometime the difference is as high as 30%

Comparing the above chart, you will see that Dolly’s peak power is at 2300 RPM at only 48 BHP, while standard engine peak power is at 3600 RPM at 74 BHP… now the question is why Dolly’s power seems to prematurely ended… certainly she is not a young girl anymore, but I am sure she should be able to out do anyone with stock engine.. :)

I hear you ask…: How come I do not know the problem in the first place… I should have known right..? I ride her every day how can I not notice it…  (I can see your smirk there Bas****d). The answer is because I never ride her hard… Dolly is at best when you ride her slowly, attentively, and she will reward you with satisfying side to side smooth and gentle rocking… (Are we still talking about car here…??? ).

I am glad now I found the problem that is half the answer… A lot of things can go wrong, The carburetor, the ignition, the engine, fuel pump, chain timing, vacuum leak etc… So I need to check it one by one… its time to play doctor with Dolly..  if you have any ideas what to check and have experience sorting out similar problem.. it will be great if you can share it down below

Cheers…