Hi I\'ve been busily rebuilding my Hurley engine. I shall be posting a full report when I\'m done explaining the problems and errors that caused the premature failure of this engine (3k miles for a £3.3k engine).
I\'m at the point where I have a collection of shiny clean ported engine components and a large hole in my engine bay. I want to ensure I have included all the little tweaks I can.
I haven\'t balanced the rotor/crank assembly. It would be nice to be able to raise the rev limit to 8.5k (car pulled stringly to 8k prior to failure) and I believe that by improving the balance that this can be achieved. I was going to balance the rotors as a pair but i\'ve realised that as its a 90° crank this will not make a scrap of difference. My question is: has anyone come up with a static balance method i can do at home that will improve the balance of my engine?
I have read in the mazda competition manual the nominal bob weight balance mass (used for balancing operation in place of rotor assembly) and the nominal rotor mass required for balancing. Can I correct the bob weight mass for the difference from nominal of my rotor mass\'s and statically balance.
I have nothing but some V-blocks and an electric drill. I was going to mass load the rotors to achieve the calculated balance bob weight mass and then spin the assembly and remove mass from the lowest point until I achieve a balance.
Has anyone tried this and can it improve matters? I am using different rotors to the originals and I\'m worried there may be a balance issue.
I wanted to increase the oil pressure also. To do this I was going to shim the oil pressure release valve spring. Has anybody done this and how much should I shim it by?
Thanks for any help given,
Jonathan
What model of engine is this? And which rotors have you swapped to?
:wave
Have you swapped the front counterweight and the flywheel and or rear counterweight to match the new rotors ? or are they the same type of rotors but "new" to this engine ?
Right. Sorry. Its a 13B twin turbo. I am using the rotors from another engine that had oil supply failure so can\'t use the crank. I do have the flywheel and pulley and can use these.
I have read that rotors cancel each other out but i\'m not sure about my 90° crank angle now (from memory this morning). If it is 180° then the counterweighs are there purely to remove the dynamic couple. I can then do a static balance with reasonable confidence. It is a shame I cannot afford to have a full balance. Many thanks. Jonathan
IIRC they are 180 on 2 rotor.
Quote from: BrettIIRC they are 180 on 2 rotor.
Right then. So if I balance the rotors as a pair then that WILL improve the balance of the engine and is a worthwhile exercise.
Looks like I shall be building a simple pair of balance scales.
Now. About the oil pressure...
but surely it is the difference in moment around the centres of gravity???
No need for any type of balancing if you ae using FD rotors with FD counterbalances and the rotors have the same letter marking. You could spin that motor to 10k on a regular basis with the right porting and turbo, and it would last a long time. With a couple of oil mods and some clearancing, you could do 11-12k easy. If you are not getting paid to race, don\'t waste your money/time for the extra 500rpms of rev you are looking for.
Thanks for your input igy, I think that I should be deciding how much balance I require in my engine. No disrespect intended but I like to reduce all forces and losses in an engine as a matter of course. Its good practice and will help with longevity.
Archbish, as I understand it the rotors balance each other but because of their offset along the axis of the crank there is a secondary couple that is balanced by the couterbalances. By balancing the rotor pair I can remove the primary imbalance. The couterbalance/crank/pulley assy should be in balance also.
When I have completed this exercise I shall post my results.
For the oil pressure increase. Has anybody done a modification in this area?I am struggling to get the roll pin out of the release valve. Its welded in so i\'m drilling it out. I won\'t be able to measure the blow off pressure until the engine is asssembled so i\'d like to know the shim size commonly used. If at all.
Many thanks.
Jon
Igy is right about the lettering on the rotors, make sure they are the same, they are balanced and marked by Mazda for that reason.
As igy says, make sure the rotors have the same letters or are only one out and thats all you really need to do, each rotor is filled with oil any way which affects the weight while in rotation so you wont be able to mimick it on a test bed very easily.
As for more revs, with a little bit of clearance on the rotors the engine will physically be able to rev more but if you have stock twins, you wont neccessarily have more power at the higher revs as you will find that depending on porting, your power probably drops off at about 8k or even less anyway, so there is no benefit reving higher.
Mine was on the rollers yesterday and the power starts to die off a little at 7500 rpm but on the road it feels like it just keeps on pulling but it isnt actually the case.
If you have a high flowing turbo (T51 etc) and the inlet porting is right then you can raise the power band.
Quote from: JON_BIRMINGHAMLooks like I shall be building a simple pair of balance scales.
It more like balancing a tyre isn\'t it? Scales will only measure the weight!
Is it just be or are Hurley engines cr@p?!
My brand new hurley engine struggle to get to 13,000 before i\'d had enough and went to rebuild it,
strange that the brand new engine had second hand housings i think
Quote from: deanflowersMy brand new hurley engine struggle to get to 13,000 before i\'d had enough and went to rebuild it,
strange that the brand new engine had second hand housings i think
I\'d raise that as an issue if I were you, if an engine is sold as new it should have new housings, unless it is specified that the housings are 2nd hand. (I had good second hand housings in my engine, but I requested that from RX motors)
when you say race clearenced rotors do you mean the clearence of rotor housing width dimesion minus rotor width dimension?
Or do you mean on the sides of the rotor at the corners?
Ive cleareced my rotors .015" deep across the sides where the bore is for the corner seals not breaking in to the side seal groove so it doesent burr it up.
A tuner told me to do this for high revs as the shaft can distort slightly and make your corners rub your side housings.
Also ive found on 2 diferent 13bs that ive stripped,the corner seal bore is a big weak spot and the apex seal groove is always wider here than in the middle of the groove due to the corner seal bore.
on 2 rotors ive seen, these weakened corners have flared outwards due to pressure on the side of the apex seal by .008" .
this is enough to rub your side housings almost.
as for balancing, ive got a crank built up with rotors and weights on, in correct possitions and i put it between centres and it does move slightly on its own weight, but like antnik said this will change when rotors are full of oil.
Quote from: rotaryart.uk.comIgy is right about the lettering on the rotors, make sure they are the same, they are balanced and marked by Mazda for that reason.
I understand this but it is always possible to improve upon manufacturing tolerances. They are more cost orientated.
Thanks
your dead right joe, always room for improvement on balancing on any mass produced crank, when you start talking about balancing to the nearest gram.
My crank assembled with rotors and weights and ligthened flywheel will move on its own weight between centres if i rotate it in a couple of possitions and just let go.
this means its not balanced without oil in the rotors.
to get it perfect you need to fill the rotors up with oil somehow
Quote from: stuart wizyyour dead right joe, always room for improvement on balancing on any mass produced crank, when you start talking about balancing to the nearest gram.
My crank assembled with rotors and weights and ligthened flywheel will move on its own weight between centres if i rotate it in a couple of possitions and just let go.
this means its not balanced without oil in the rotors.
to get it perfect you need to fill the rotors up with oil somehow
As I understand it the crank is 180° (i thought it was 90° at the start of this thread). Therefore each rotor assembly balances each other. Now as the amount of oil in each rotor will be the same (neglecting acceleration/deceleration whn I understand it slops forward and back) and the seals/springs/corner seals will be in almost perfect balance due to their dimensional accuracy. That only leaves the cast rotors. Now mazda grade these by letter, I don\'t know the difference is mass across each grade but by simply balancing them the same as a pair then I can be certain i\'m improving the balance.
The counterbalances on the shaft are there to remove the secondary couple forces only from the rotating assembly (rocking forces).
Alhough these could be used to remove mass from when dynamically balancing the assembly. It is better to balance the rotor assemblies first.
enquire about getting the full crank assembled with flywheel, rotors, counterweights, balanced at a crankshaft balancing specialist to get some good advice.
Im sure they wont have ever balanced a rotary ecentric shaft before, so it may be a novelty for them which normally creates interest.
something different from the normal crankshaft balancing on piston engines.
All i have ever balanced are grinding wheels and helical rotors between centres, but thats with just moving sliding bobweights around until the wheel or rotor doesnt move in any angular position on its own weight.
The rotors we made are for compressors, superchargers, pumps etc by the way at Holroyds machine tool and rotors.
Quote from: stuart wizyenquire about getting the full crank assembled with flywheel, rotors, counterweights, balanced at a crankshaft balancing specialist to get some good advice.
Im sure they wont have ever balanced a rotary ecentric shaft before, so it may be a novelty for them which normally creates interest.
something different from the normal crankshaft balancing on piston engines.
All i have ever balanced are grinding wheels and helical rotors between centres, but thats with just moving sliding bobweights around until the wheel or rotor doesnt move in any angular position on its own weight.
The rotors we made are for compressors, superchargers, pumps etc by the way at Holroyds machine tool and rotors.
Yes. I\'ll have a look and see if I can call someone tomorrow. Time is short now if Pip gets my housings in tomorrow. Nice long weekend building and commissioning... :)
I\'ve got a nylon cutting board to chop into V-Blocks to check the final balance and a bit fabrication work to make a beam balance and i\'m done. Just the \'simple\' job of assembly after that.
I\'m thinking of clearancing the rotors now. I have a rotor that has touched the housing (oil pickup blocked (don\'t ask!) and lost the oil film at high revs) so I know where to relieve them.
It would be great to be able to pull 9000rpm in 1st. Great advantage at the strip perhaps if my porting is up to scratch.
Thanks for all the advice gents. Especially to a non-member :rolleyes:
Right.
Well Pip got the goods in and I\'ve built the engine. I balanced the rotors to within 1 peanut at my local pet shop!!
Sounds dodgy but they were a £2k set of scales. Resolution was 5g so I improved that with peanuts. One of the rotors was about 8g heavier than the other.
I\'ll be installing the engine tonight and tomorrow.
Quick question. Do you fit the engine back in the bay with the engine mounts on or off? I had to remove the mounts before sliding the engine forward from the gearbox but the mazda manual has them on.
Do I need to jack the gearbox at the front to tilt it?
many thanks,
Jon
I have tried to help out on a few engine installs. And what people do is: jack the gearbox up, almost as far as it will go. Put the engine in with the mounts already attatched, and slide the fella in at an angle :p
Cheers. I\'ll try that tonight. I jacked the box up level last time and it was a struggle to get it to disengage.
Where in B\'ham are you?
John
I think the best way to get the engine in with the mounts on is get the engine in the bay as far back as it\'ll go. Then put the hoist around the bellhousing of the box and lift it and get a bar in under the engine and prise it back so it dropped into the cups for the mounts, worked for me with just about everything on the engine.
Taking it out I put the hoist around the bellhousing and prised it out over the cups where the mounts sit.
Hi Jon. I\'m in Sutton Coldfield. I\'m dropping the engine in tonight. Last night was R&R!
You don\'t fancy coming over do you? I would welcome your help.
Hi Bucky. I\'ll try that as it was a tight fit just to remove it.
Jon
Can\'t do tonight but I\'ll come over some other time it you need a lift or anything, but don\'t expect me to know what I\'m talking about.
John
Update!
She started up first time and ran like a good un...whilst pumping 4 litres of oil onto the floor!
After I\'d done up the oil pipe union she ran again. Very smooth. Then fouled her plugs and started running rough! ( 1 hour at idle)
All that 2 stroke oil in the fuel isn\'t helping but she\'s ok now.
I\'ve learnt alot so I\'m going to post a technical thread explaining it all.
Thanks for all the info over the past few months.
Jon
excellent - congratulations.
Quick update. She\'s lost front rotor compression...all my whinging about Hurleys and my engine hasn\'t lasted more than 2000 miles!!
She does have phenomenal balance though. You struggle to tell she\'s running when you place your hand on the engine and no resonances up to 8k either.
Hasn\'t used any appreciable oil during this period and holds 7kg.cm² oil pressure with 5mm shims in the regulator.
I\'ll let you know what I find when I break her down soon. She was making a slight clicking noise from the block area so i supect I will have corner or side seal damage caused by my porting not being correctly radiused.
Jon
Quote from: Jonathan_FThe counterbalances on the shaft are there to remove the secondary couple forces only from the rotating assembly (rocking forces).
Alhough these could be used to remove mass from when dynamically balancing the assembly. It is better to balance the rotor assemblies first.
Do you know if they use the counter balances for dynamically balancing the assembly? If they do, then doesn\'t statically balancing the rotors mean that the assembly needs to be rebalanced?
MMM i like to fit FD engines with the Mounts off, Its just somthing else to get snagged on somthing when your mating it up to the Box. For how easy they are to get in after theres no point in struggling. But then i did also refit my engine with the down pipe off :)
Quote from: GrizzlyMMM i like to fit FD engines with the Mounts off, Its just somthing else to get snagged on somthing when your mating it up to the Box. For how easy they are to get in after theres no point in struggling. But then i did also refit my engine with the down pipe off :)
I do too. Mounts off and downpipe off. Slot it into gearbox and tighten a few bell housing bolts. Then loosely fit downpipe. Then fit and tighten mounts. Drop engine and box down and finish off the other few joints and connections.
Start engine.
Smoke cigarette. :cool
Quote from: MaveDo you know if they use the counter balances for dynamically balancing the assembly? If they do, then doesn\'t statically balancing the rotors mean that the assembly needs to be rebalanced?
My thinking, and i\'m not 100% sure, is that the crank, front pulley, front pulley bolt,flywheel and nut,counterweights and clutch should be a balanced (dynamically) assembly. The rotors just need to weigh the same as each other.
The rotors are at 180° to each other so balance each other. The secondary couple size will be determined by their mass. Now mazda use a wide range of masses for rotor pairs for any given crank. And experiance I\'ve gained myself says that the degree of accuracy needed for secondary couples is less than for primary imbalance.
My engines very smooth externally. Although not running well!
Jon
Quote from: Jonathan_FMy thinking, and i\'m not 100% sure, is that the crank, front pulley, front pulley bolt,flywheel and nut,counterweights and clutch should be a balanced (dynamically) assembly. The rotors just need to weigh the same as each other.
Jon
That is the only written way to do it,however my engine balancer insists on having the rotors as well with old bearings in.......... :Typing
Quote from: oldoneThat is the only written way to do it,however my engine balancer insists on having the rotors as well with old bearings in.......... :Typing
Spanner + works..
He\'s probably just checking their still balanced as a pair. Unless he\'s a full on proper balancer and he\'s making bob weights.. but then he\'d ask for the seals and springs etc and have to guess the oil mass in each rotor...
What do you rev to Oldone?
Jon
Hurley\'s have asked me to edit out the personal references made about people being in hospital etc as this is only hearsay and as said personal.
They also state that this guy has never been a customer and that the only contact they have had is that they measured a few things on his engine as a favour and that all the ancillaries on this engine have been changed or modified i.e. Turbo\'s, Power FC etc, also that apparently the engine has been removed to perform some of this work and therefore the engine would never be warranted by anyone due to the engine being heavily played with long after the engine was built.
One last thing is that they feel it unfair that the measurements of their tips and groove dimensions are being banded about when Hurleys have never ever disclosed this information to anyone out side of their company.
Jon if you wish to discuss this further please ring the club address and leave a number
Quote from: clive
One last thing is that they feel it unfair that the measurements of their tips and groove dimensions are being banded about when Hurleys have never ever disclosed this information to anyone out side of their company.
Jon if you wish to discuss this further please ring the club address and leave a number
Mick is correct. I\'ve stated the changes and the fact that the engine was running lean.
If he is upset about his companies inability to machine components correctly, or his companys use of components that have been machined incorrectly by a third party, then I apologise for publishing this information.
Jon
Here are some shots, before and after I removed the secondary butterflys. My polished rotors (yes I balanced them after!) And the piece of invoice paper some kind soul put in the oil to block the pickup. And a cool shot of the rex outside work. Night mode on the mobile played some tricks with that one.
Jon
Damn. Tried to upload some pics but too large. Need photoshop.
I\'ll try again another time.