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Pedal Smasher
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Discussion Starter #21
Thomas, thanks a ton for that breakdown of what is happening. It makes sense to me. I hadn't looked at the equation that would have dictated the centrifugal force and kept thinking about linear vs nonlinear springs and how that could influence this design. I think it's good to know how this rotor works, so it doesn't come as a surprise if the engine loses all spark for a while if the rev limit is reached. For use as an accidental over-rev safety, it's perfect.
 

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The above fits a GT fine? It just looks different; but, of course, it would have to, support the added functionality.
I do not personally know. I was thinking of buying one to try out, but the shipping cost to me in Canada is $17.10, almost as much as the rotor itself at $18.30, But it sounds like others have used them.
 

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Pedal Smasher
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Discussion Starter #25
What I've been seeing shows that these rotors are designed for 4 cylinder Bosch distributors. So, I believe they will work. I'm looking into a few other things before ordering one from autohausAZ, best price I could find for a 6,800 RPM rev limit. It seems Bosch used these on BMW 2002's, Porsche 914's, 912's, 911's, and pretty much anything by VW. I have a feeling that the only reason why Opel never saw this is due to cost. The ordinary ignition rotor would be cheaper.
 

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Opeler
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I used one I found in a drawer in my grandfathers workshop in my kadett c during the nineties when I used it as a Daily driver.
I believe it was used in my uncles Volvo Amazon rally car in the seventies,
 

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Opel Rallier since 1977
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What I've been seeing shows that these rotors are designed for 4 cylinder Bosch distributors. So, I believe they will work. I'm looking into a few other things before ordering one from autohausAZ, best price I could find for a 6,800 RPM rev limit. It seems Bosch used these on BMW 2002's, Porsche 914's, 912's, 911's, and pretty much anything by VW. I have a feeling that the only reason why Opel never saw this is due to cost. The ordinary ignition rotor would be cheaper.
Or it may be that Opel stuff just does not tend to break up at high revs. I used to rev to 7700 RPM at every 2-3 shift and sometimes to 8200-8300 RPM, in my rally engines. Never did anything special to the crank or rods which are forged for the ealirer 1.9L. I did use TRW forged or Heppolite cast pistons. Stock timing chains and gears. Average sustained RPMS were probably around 6200 RPM. No odd wear that I ever spotted.
 

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Pedal Smasher
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Discussion Starter #28
Valve float is a different animal than just spinning at high RPMs though. When does valve float start on a typical CIH?
 

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Opel Rallier since 1977
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All I can say is that I never had valve float. Probably hit 8400 RPM once or twice. But it is not an phenomenon that you can just say 'it is always this or that'. It is highly dependent on a lot of factors but most of it is:
  • weight of parts
  • velocity of cam profile
  • acceleration of cam profile
  • valve spring rates
  • angles of rocker arms
  • RPM
We typically think of the valve launching off of the top of lobe and floating in space for a bit until the spring pushes it back down and it 're-contacts' the lobe. But more often it is due to the accelerations of the valvetrain inducing strong vibrations in the springs, which causes the valvetrain motion to 'surge' all over the place with the spring vibrations.

For what I was doing, it was the Isky Ultra Super Comp, with some fairly modest valve springs. The old Isky cam lobe designs are pretty sloooow in the profiles, giving us lower velocities and accelerations than more aggressive cam profiles. So for my case, it did not take a lot of spring to keep the spring vibrations low due to that old sloooow lobe design.

Here are a couple of instructive videos on spring vibrations. When the vibrations get going too hard, this is the surging type of behavior that happens, and the 1st video actually shows the spring breaking near the end. The cures are higher spring rates (which moves the sping's resonant up higher and further away from the inducing force's 'frequency'), spring dampers, and multiple springs (double and triple) where each spring is wound differently to have a different resonant frequency. Beehive springs with their progressive spring rate is another technique used.

 

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Shipping was free to me; so I went ahead and ordered one. Scheduled to arrive Jul 20. I'll let you know.
I received the rotor. I appears that it will not work for me because I have a Crane ignition with the optical trigger, and there's interference between the rev. limit rotor and the light source nodule that fits around the shutter. It might work for other folks; but it's hard for me to tell.
 

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Pedal Smasher
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Discussion Starter #31
I received the rotor. I appears that it will not work for me because I have a Crane ignition with the optical trigger, and there's interference between the rev. limit rotor and the light source nodule that fits around the shutter. It might work for other folks; but it's hard for me to tell.
Have you considered changing to Pertronix?
 

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I have not considered changing to a Pertronix. What I am in the process of doing is going to fuel injection. When I get that running I believe there are a couple of choices on how to rev. limit via fuel, with the microsquirt. Initially, this will be a fuel only conversion, retaining the current distributor, and inductive ignition.
 

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Pedal Smasher
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Discussion Starter #33
Mark, if I was going to install a microsquirt efi system I would consider a couple of additions. Classic Retrofit has a programmable capacitor discharge ignition setup that would work well with an Ignitor. While a tad expensive, it would make it possible to program the exact advance curve I wanted. It's based on the Bosch CDI that Porsche used.


I'd also consider using Fuelab's electronic fuel pressure regular and corresponding fuel pump.


Both of those might seem like overkill but I'd have active control over the afr, fuel pressure, and ignition. And it could be done on an oddball engine like the CIH without needing to create any parts. The Opel FI intake manifold can be found for sale in Germany or the RetroJect TBI could be used I'm thinking with the microsquirt.

Again, these might be overkill for some but it's worth thinking about.
 

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Opel Rallier since 1977
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When I get that running I believe there are a couple of choices on how to rev. limit via fuel, with the microsquirt.
FWIW on my Mistubishi Starion (2.6L turbo with 14-15 psi boost), they used a 100% fuel cut strategy to prevent damage when any engine knock was detected. At full boost, that fuel cut was an extremely violent event! No damage, but it shook the car HARD to hit that knock limit, as it would go on and off rapidly. If you are not- turbo'd then maybe not so violent, but it may be worth your time to explore the options of fuel or ignition cut.
 

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FWIW on my Mistubishi Starion (2.6L turbo with 14-15 psi boost), they used a 100% fuel cut strategy to prevent damage when any engine knock was detected. At full boost, that fuel cut was an extremely violent event! No damage, but it shook the car HARD to hit that knock limit, as it would go on and off rapidly. If you are not- turbo'd then maybe not so violent, but it may be worth your time to explore the options of fuel or ignition cut.
When I looked at the Microsquirt manual, it appears to me that there are two cut options, hard and soft. The hard cut seems like what you're describing. In the soft cut, at a configurable lower limit they start randomly cutting injector firing, with increasing frequency of cutout until you reach the upper limit. At least that's the way I read it. Also, I can't quite remember if the upper limit was configurable, or a fixed number above the lower limit. In any case they seemed like they'd implemeted a reasonable soft limit strategy, which should avoid what you described above.
 

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That sounds like it would be better. But one good thing about the 'violent' fuel cut upon detotation.... I never did it more than twice! I stopped the car and cut the boost back 1 psi LOL

With the earlier Opel stuff, with the forged rods and crank, I don't think I would bother with a rev limiter....
 

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Mark, if I was going to install a microsquirt efi system I would consider a couple of additions. Classic Retrofit has a programmable capacitor discharge ignition setup that would work well with an Ignitor. While a tad expensive, it would make it possible to program the exact advance curve I wanted. It's based on the Bosch CDI that Porsche used.


I'd also consider using Fuelab's electronic fuel pressure regular and corresponding fuel pump.


Both of those might seem like overkill but I'd have active control over the afr, fuel pressure, and ignition. And it could be done on an oddball engine like the CIH without needing to create any parts. The Opel FI intake manifold can be found for sale in Germany or the RetroJect TBI could be used I'm thinking with the microsquirt.

Again, these might be overkill for some but it's worth thinking about.
That's interesting; I wasn't aware of that electronic pressure regulator. However, I've gone a slightly different route. After watching for a bit, I found a good price on a sort of new (only used once for bench test with fuel, seller said) Hyperfuel 40004 Command Center 2:
Command Center 2 – HyperFuel Systems
And it has a pressure regulator built it. Not as nice regulation, I think, as what you were showing, but enough to do the job. Pluses on the hyperfuel system, I thought, were:
compact size
no fuel return line (although you still need a vent line back to the tank)
built in pressure regulator
pump submerged in (small) surge tank for cooling & noise suppression

As far as the CD ignition goes, I think it will be simpler, at least for now, to stick with a distributor setup. And for that to work with the microsquirt, as I read the manual, you need to stick with inductive. Less than full control, for sure, but maybe less of a giant step.
 

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Just a note to be aware of: the line back to the tank for this system IS a return line, not a vent line. Not that it matters much about the function.... a new line and tank fitting is needed.
I re-read the instructions; I think now maybe you're right. Earlier, I had thought the specs's were somewhat ambiguous. Then, in what seemed like their FAQ section, I saw:
The 2nd generation FCC is much improved, but some vehicles are just hot underhood. But if the FCC is mounted well away from the exhaust (I’ve seen them installed right next to exhaust) you should be OK. And while you don’t need a fuel return line, you do have to run a vent line to the tank, which is almost exactly as much work.
And I thought the bold indicated it was a hyperfuel response. Maybe not, though, could be part of a customer question/comment. But the above at least explains why I thought it was a vent.

Maybe I'll contact hyperfuel. The guy I talked with a couple of times seemed nice and straighforward.

I guess for me it does make some difference. If it were a vent line, I'd probably go with a soft line. If it's really a fuel return line, it might make me more inclined to run a hard line
 

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I see the above was from a vendor site, not the manufacturer; probably it's wrong. But I did post an request for clarification with the manufacturer.
 
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