Motor Rebuild – (hot-to-trot)

[Doc Fizzix]

This is from Philbo's write-up

Lighter flywheels are a traditional way of gaining acceleration, as less power produced by the engine is spent overcoming inertial mass in the drivetrain. In gear acceleration can be much improved with a light flywheel, however go for an ultra-light flywheel and you’ll have a very lumpy idle and stalling the car will be simple. The standard Elan flywheel is 5.5Kg and probably over engineered for our car as it was probably specified for the heavier Isuzu Impulse RS. A 4Kg flywheel apparently gives little or no difference in feel, perhaps a flywheel of around 3.4-3.6Kg would be ideal? Replacement flywheels for the Elan seem to be hard to come by, though some companies can grind weight off the existing flywheel. Fidanza is a recognized name that makes aluminium flywheels, although I’m currently trying to find UK-based

The Fidanza states that flywheel has the following weight: 8.5 lb, lbs = 3.855 kilogram

[Doc Fizzix]

Now that the body rear is all done, we focus on the upgraded engine build up.<br><br>I posted pictures of the JE pistons, now its turn of the custom made competition flywheel which is almost half kg (1 pound) less in weight than the stock one. <br><br>The stock flywheel is made of cast iron while the custom competition flywheel is made of steel after thorough tests at phasmatographer, therefore the less weight which was our target afterall.<br><br>Front and rear view<br><br> <br><br> <br><br><br>And a comparison with the stock one<br><br>

[Dave M]

Not to poop on this party, but I question some of this stuff....

Don't tell that to Dave_M or Costas, Dave has the same flywheel and Costas used the same thinking with his.

Hey. no pooping on my car! It's been handicapped for a year now...it's got it's own issues.

Since my brain is buried in tax law right now, I don't have much capacity to dig into the physics of the springs too deeply, but here's a question:

If the compression stroke produces a cylinder pressure of somewhere around 150-175 psi, wouldn't this help keep the valves closed anyway? Seems the valves could "float" until the cylinder pressure reached the same psi as the intake side. Then the pressure difference would close the valve on its own.

[Doc Fizzix]

Dave, I will be dropping off parts with my mechanic today and I will talk to him about this.


UPDATE - see bellow

[Doc Fizzix]

Ok, I am wrong from above

Just got back from the mechanics shop. The problem is not with the compression stroke but on valve overlap strokes. With the increased boost pressure pushing the intake valve down it becomes harder for the intake valve to follow the cam lobe (causing valve float). Yes, greater spring pressure is needed for higher reving motors in order to prevent valve float at high rpms but they are also need with the increased boost pressure for the same reason, valves can begin floating at lower rpms because of the backside pressure of the boost on the valve. Like anything, you want to find a balance, you do not want more spring pressure than is needed but this pressure has to be large enough to compensate for the increased boost pressure. That is why I am having my valve springs custom made, to match the amount of spring pressure that is needed for my application.

THis is what I got from my shop

[Monty]

Thanks Monty. I paid $329.00 + $15.00 shipping so a total of $344.00 US

Monty, are you ready to sell me that Quaife yet?

That`ll be going in the gearbox early next year if dico pulls his finger out

what are u doing about a clutch?

[Doc Fizzix]

I have found a Quaife at last

We will have to compare note on this.

I am using eh stock clutch and pressure plate

[Monty]

I have found a Quaife at last

I`m sure i read that there was a problem with the Fidanza fly wheel was it something to do with the finish

[Doc Fizzix]

I'm sure i read that there was a problem with the Fidanza fly wheel was it something to do with the finish

Only if you are using something other than stock

[Nige]

Can't recall who but I do remember someone saying they had to have the surface of the flywheel skimmed as the clutch slipped. Thats why the last group buy was aasco flywheels rather than fidanza.

[Doc Fizzix]

Dave_M had to have his re-surfaced but this is only a problem with some after market performance clutches. I had read the same thread and did a lot of home work before I bought this flywheel. Fidanza even told me that they had problems with several after market performace clutches but never with stock and it was designed to work with the stock clutch. Talked with several Isuzu owners who are using the same flywheel and have never had a problem with the stock or an after market clutch so I feel it will work just fine for what I am doing. I will still be using the stock clutch and pressure plate

[Ashaman]

Thanks Dave, exactly my thinking (which admittedly may not be correct). If you were having a problem with this, I would also think you would totally hammer your valve seats anyway. (I haven't seen or heard of this happening yet in spite of some pretty high boost levels)

Thanks M100 for explaining the reasoning behind it also...I just couldn't imagine what it was based upon, but now at least I understand the thinking. 'Course, I also still disagree, but hey..if you have the money and are in there, why not. However, I think your "illustration" is flawed if it was an issue of forcing air on a single valve, in practice that will not happen.

I only piped up because you said it was necessary, and I do not think it is. So, I don't want everyone to think that "Oh, if I want to run 20PSI I have to buy $550 valves. I don't think there is enough evidence to make this blanket statement, and to me, the evidence is to the contrary.

Regaring the primer on mass, I already understood the flywheel reasoning. That doesn't negate my warning now though does it? Everything I said is absolutely true on that. My point was that rotating mass isn't inherently a bad thing, there are also benefits to having some there, and penalties to having to little. Now, if you have the same one Dave is using, then great. You have no worries about going too light like I said now do you?

My point here is to prevent misinformation from being posted on the board, that is all. I think that if we state you MUST DO "X" before blah, blah; we should be sure that we know this to absolutely the case.

I personally do not like wasting time and money on something that wasn't really necessary and does not yield a real-world benefit, and think there are probably others with the same thinking. That is all.

There are undoubtedly guys out there who know more than me on this stuff than me. However, those same guys should then be able to give specific benefits to doing these things (preferably in terms of a power gain) and/or penalties to not doing them as a result of the research that determined it was necessary.

[Doc Fizzix]

Ashaman, please do not take this personal but I want to respond to some of your comments because I believe you may have misinterpreted things and made some incorrect statements. This is not an attack and I am only addressing your posting so please do not be angered.

However, I think your "illustration" is flawed if it was an issue of forcing air on a single valve, in practice that will not happen.

I strongly believe that you are no seeing a clear picture on this subject and this is not my original argument it is the discussion of many other people who know a lot more than me, I believe this is a proven reality and aspect of all force air induction vehicle. Any "forced air" system is going to have to deal with air pressure pushing on the back side of the valves causing the valves to want to open and float at slightly lower rpms than normal, this is a real situation that you MUST make sure you deal with it. If your valve springs are strong enough for your application or level of boost then do not worry about it, but on my end, since I will be running more boost than orginaly designed, I am very concerned that there is/or may be a mismatch between the stock valve springs and the boost that I want to run. A quick calculation of the backside area of the valve and the level of boost pressure anticipated answers this question and for what we have figured I need a little stronger spring.

I only piped up because you said it was necessary, and I do not think it is. So, I don't want everyone to think that "Oh, if I want to run 20PSI I have to buy $550 valves. I don't think there is enough evidence to make this blanket statement, and to me, the evidence is to the contrary.

Ashaman, please do not put words in my mouth, I did not say you "HAVE" to buy $500.00 valves. I only stated that I was getting new valve springs made because we do not feel the stock ones are matched for my application.

I feel strongly that if you run 20 psi of boost you will need to seriously look at the valve spring strength. My price is very high only because I am getting titanium valve retainers with my set-up as originally stated in my thread. Less mass = greater acceleration

This thread is not about the products that you "have to buy", this thread is just about my rebuild, what I am learning, and what I am doing on my end so I can share it with others and they can use this information as they see fit.

I think that if we state you MUST DO "X" before blah, blah; we should be sure that we know this to absolutely the case.

Please do NOT suggest that I am telling people what they "must" do, NO WAY, I am not doing that, I am only sharing my rebuild experience. My only blanket statement is the following: You need to make sure your valve springs are strong enough when you are going to be pushing more air into the system than it was originally designed to handle, to ignore this real effect on the valves is potentially a very big oversight. I apologies but my statement in my original posting was the words from Don, the owner of R/D Valve Springs, I was not very clear about that and I am very bad at typing and writing so it may have come accross as me "telling" but that was not the case and I am very sorry if you misunderstood that.

[Doc Fizzix]

Removed - already discussed above

[Doc Fizzix]

However, those same guys should then be able to give specific benefits to doing these things (preferably in terms of a power gain) and/or penalties to not doing them as a result of the research that determined it was necessary.

Not everything is about power gain, somethings have to be done in order to make sure the motor work properly as designed, if the valves do not have enough spring tension to compensate the boost pressure you will get valve float at slightly lower rpms causing a loss in potential power and even damage to the motor in extreme situations, simple and true!

I personally do not like wasting time and money on something that wasn't really necessary and does not yield a real-world benefit, and think there are probably others with the same thinking.

You can ignore these thing if you want but I am going to look out for my investment and listen to my mechanics on this issue and I also recommend to anyone else that is planning on increasing there boost to 1.2 ~ 1.5 atm to consult a good mechanic just to make sure that their system can handle the increased boost. (I am not saying it can't, but I am saying just make sure, what is so bad about that?)

It may be that you can run your "stock" valve springs at 1.2 ~ 1.5 atms of boost but that is not what we are finding on my end and I would rather be safe than sorry, we believe that we need a little more valve spring tension.

[Doc Fizzix]

Removed - already discussed above

[Costas]

I am really extremely busy lately and I didnt have time even to check on LEC for a week or so.

Tried to foloow missed posts in this thread but I got lost...

my 2 cents as far as I know out of my experience and countless hours of talking with my mechanics:

Flywheel: I ve read (philbo?) of lightening the flywheel over 1pound and actually lightening for 4 pounds! If you do so you have to treat the crank acoordingly and balance it with the flywheel on. Nevertheless such a lightening will destroy your engine efficiency since it will raise RPM faster that you can shift gears.

What I realized of this whole thing is that lightening the "moving parts" of the engine (Flywheel, rods, Crank) gives you not just faster acceleration, but what it really benefits is a major increase in Torgue! (torque?). Most ppl ask me what is the horse power of my Elan but none asks me what torgue it produces..... I tell you, the happy feeling I get everyday I drive Sh4rk is because of those 42kgm of torgue which is over double of stock if I am not mistaken. Big hp and big torgue can benefit from lightening for efficiency but if you overdo it you will regret the moment you did it as you wont be able to enjoy it.


Now I read an argument about valves and PSI and didnt manage to undesrstand whats going on, what is 20psi in Bars?

Anyways, about the valves, I used the car even at 1.7 boost pressure
(400hp without NOS) and the valves work fine, perfectly may I say!. But if you want to increase HP through an increase in RPM, then you NEED harder valve springs.

Advise : Dont tune over 1.2 boost pressure without forged pistons-rods.

Costas.

[Doc Fizzix]

Flywheel: I ve read (philbo?) of lightening the flywheel over 1pound and actually lightening for 4 pounds! If you do so you have to treat the crank acoordingly and balance it with the flywheel on. Nevertheless such a lightening will destroy your engine efficiency since it will raise RPM faster that you can shift gears.

Thanks for your input Costas, how much did you remove from your flywheel? and from where? Rotational inertia depends MORE on where the mass is located and not the total mass. I am not attempting to remove mass as you did when you made yours but I am replacing with a Fidanza flywheel that is already balanced and ready to install. I can have the crank and flywheel balance together and in all honesty I should make sure that I double check the balance anyways.

The Isuzus heavy flywheel is most likely one of the reasons the Elan has such good gas-milage on the highway, I know I am going to be pissing that out the window but I only use the car to shoot around town on weekends. With the lighter flywheel the car will rev quicker and it will fall from the revs just as quickly without the extra mass of the flywheel to keep its momentum, but as I said, it all depends on what you are trying to do.

Dave_M, we need to hear from you about the flywheel since you are running the same one. What has your experiance been? How are the revs in the low gears? Any comments on your end

[Doc Fizzix]

Here is some more info on the Fidanza flywheel:

The stock flywheel is about: 12.125 lbs = 5.5 kilogram (from Philbo's write-up)

Fidanza list this same part number for two vehicles and there are two weights listed:
Isuzu Stylus (4XE1 motor) 8.5 lbs = 3.86 kilogram
GEO Storm 9 lbs = 4.082 kilogram

Both vehicles take the same part number but I will not know if the flywheel is actually 9 lbs or 8.5 lbs until I get it. I called Fidanza on this and they told me that the flywheels are identical but there may have been a misprint for one of the weights.

UPDATE - The actual measurements on on this page
http://www.lotuselancentral.com/forum/v ... 5562#65562

So it is NOT 50% lighter, at most it is 30% lighter or if the flywheel weighs 9 pounds then it is only 25.77% lighter. Keep in mind that the stock pressure plate and clutch are being used so there is plenty of mass still on the crank to give it the inertia it needs.

Using some simple physics the rotational inertia for a disk is I=1/2mr^2 (where I is the rotational inertia, m is the mass, and r is the radius of he disk)

Since the rotation inertia of the flywheel is more dependent on the radius of the flywheel (since from the formula the radius is squared) I am confident that even a 30% change in mass of the flywheel will not cause a lot of trouble with surging and stalling. The actual change in rotational inertia is going to be less then the 30% for the lighter of the two possible weights of the Fidanza flywheel when you figure the pressure plate added to the system. I could work out the math but I am only guessing it would show about a 10% or less change. When I get the flywheel I will mass everything up and actually give some sold numbers.

But, I feel the difference will be just enough to give the car a little more torque as Costas is saying in his discussion

[Costas]

Thanks for your input Costas, how much did you remove from your flywheel? and from where? Rotational inertia depends MORE on where the mass is located and not the total mass. I am not attempting to remove mass as you did when you made yours but I am replacing with a Fidanza flywheel that is already balanced and ready to install. I can have the crank and flywheel balance together and in all honesty I should make sure that I double check the balance anyways.

Well to be more accurate, I didnt "remove" any material from a stock one but after countless tests on phasmatographer (to test materials) DSP built for me a Custom Competition one that is lighter than the stock one of about 650grams (0.65 kgr or about 1.3 pounds). The shape is almost the same (the outter ring is different at the screwpoints) but of lighter and better material. Proven in action....

Greg was very strict on not making a Flywheel that would be lesser in weight over 1.5 pounds than the stock one.

Here is a picture of the custom made and the stock one next of it.

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