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'Classic Retrofit' Bosch CDI+ Replacement Ignition Unit (Spark Box)


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Hello folks,

 

I am struggling to keep this a secret now so I'm spilling the beans....

 

I've started a new company to develop and supply Porsche Bosch CDI replacement units and modern replacement Porsche fuse panels - the company is called Classic Retrofit.

 

For the last two years (!) I have been using my defense and aerospace electronics firm to develop a plug and play replacement for the Bosch CDI box fitted to 911's between 1969 and 1983 and also later 930/911 Turbo cars. It's nearly ready!

 

The brief was that it had to look original but that it should also have a few tricks up it sleeve. Well, firstly, it will be offered in a CNC aluminium replica case but it also fits in the original case. We will offer a refurb service if an original case is required.

 

Here's a CNC case in my SC:

 

cdi_in_car.jpg

 

Inside the box:

 

cdi_pcb.jpg

 

 

So what tricks are there to be had? Well so far we have:

 

  • Hard RPM limiter with adjustable ignition cut schemes
  • Soft RPM limiter with adjustable ignition retard
  • Launch RPM limiter
  • Double spark at all RPMs
  • Max RPM tell tale
  • Shift Light output
  • Clutch pedal input
  • Tacho calibration
  • Upgradeable through firmware updates

 

There's some software you get for setting the unit up with a laptop. The diagnostic connector for the unit is in the engine bay photo above - the thing with the blue cap.

 

 

software.jpg

 

 

Anyhow, you can read more about the development on the Classic Retrofit website.

 

p.s. Website is a bit of a work in progress. The fuse panel stuff is there too. I need to put a discount code up for the paypal so please don't press it yet!

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Thanks everyone, it has certainly been an interesting and fun project so far.

The graph shown above is the advance that my SC is running with 97 Ron fuel. At peak, I'm at 30 degrees advance, 10 more than the standard distributor advance with no hint of detonation. I'm booking a rolling road session soon to get the best out of the mapping. Will post results up when I get them.

Soft Rev limiter is a joy. I run a plain 3.2 rotor arm and the box does the limiting. No more brick wall, just a gradual loss of power. Combined with the shift light, it is pretty effective. The 'launch control' is a lot of fun. Hold clutch and floor the throttle. Engine limits at 'launch revs', release clutch and go!

We have some guinea pigs out there including Mark (SilverWT) from this forum so many thanks for their test mule services!

SCud, yes it is still a capacitive discharge ignition system, just like the original but with double sparking and a microprocessor brain.

David, the 6 pin Classic Retrofit CDI+ Bosch replacement ignition box will fit straight on your '84 Turbo. I think the later 8 pin CDI only appeared on the very last Turbos.

Pricing will be around the £800 mark. Although this is more than say, MSD, you can fit ours in half an hour and there is no change to the wiring loom. By comparison a garage may charge up to 6 hours labour for fitting most aftermarket units due to wiring loom adaptation, mounting the unit etc.

Ours uses the original coil too so there is nothing else to buy. This is specifically designed for the 911 to 'just work'.

Tea boy, witchcraft nearly always involves oil so I think you might be wearing the pointy hat!

Great stuff, you put this on DDK?


Hi Nige, yes soon to go on DDK, gotta sort something out with Bootsy.

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We have some guinea pigs out there including Mark (SilverWT)

Yep, I think Zinn twin the Elder was the first real car to run a test late last year and now has quite a few trouble free miles on an early production version. Excellent well thought out bit of kit :bowdown:

 

Not yet fully exploited the performance potential, so some more fun ahead :revs:

 

Mark

 

 

 

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Hi Ian,

 

First of all, the unit is not actively being marketed as a 'performance product' but there are a number of factors that it can help with, that do play a role in the performance of your car.

 

1) If your distributor weights/springs are worn, gummed up etc, you may not be getting the advance curve that Porsche intended. By locking the weights and letting the unit control the timing, you will get a perfect advance curve. We have a unique way to lock the distributor weights that takes less than five minutes and you don't need to take it out of the car.

 

2) The SC in particular was very conservatively setup by Porsche timing wise. If you run decent fuel, you can advance the timing and get more power. This is common knowledge amongst 'tuners' but always with an ear out for knock (no knock sensor on CDI a cars). Of course, on a standard car, you can turn your distributor physically to get the performance boost. Only trouble is, you'll be idling at 2000 revs like an idiot. Our box allows you to put in a custom curve which gives the extra power with a sensible idle speed. Also, if your car has other mods (SSIs, cams etc) it may well respond well to a different timing curve.

 

3). The mechanical rev limiter on the SC is a crude throw out weight built in to the rotor. This cuts all ignition dead. As Mark put it, when it activates it feels like the engine has gone bang, not nice. When it comes back in, there is a good chance of a massive backfire due to accumulation of fuel in the chambers. Our unit uses a 'cut X sparks out of Y' scheme. It is programmable but I use cut 4 out of 5. In other works, every fifth spark is still firing, preventing the backfire and cylinder washing of the original design. This 'feels' much nicer than the brutal mechanical method. We also have a 'soft' rev limiter that backs off the advance, rather than cutting sparks. This can be set up just before the hard limiter so you get a slight decrease in power prior to the spark cut. Combined with the shift light, this is much more user friendly.

 

4) The launch control allows you to set a rev limiter that is activated by a switch and a rpm threshold. On my car, my clutch pedal activates this and as long as the revs are below 1200 rpm, launch is enabled. I can now floor the throttle and the engine is held at the rpm of my choice. As soon as I release the clutch, the limiter is cancelled. Oh, and you can get flames out the exhaust which is every schoolboy's dream.

 

I'm due to do a rolling road in a few weeks with a standard CDI and ours and will post the results.

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Good work Jonny: the market is wide open for this sort of product. I think better to get people to contact you in person to discuss this unit, and build the info available on the website rather than letting this turn into a trade ads thread where only IBers can see the information. Nice one.

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Good work Jonny: the market is wide open for this sort of product. I think better to get people to contact you in person to discuss this unit, and build the info available on the website rather than letting this turn into a trade ads thread where only IBers can see the information. Nice one.

Noted JG. The website is a bit of a work in progress at the moment . I will be putting up more info on the CDI+ soon. I am working on a spec sheet and manual.

 

Feel free to contact me on info@classicretrofit.com

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Hi Jonny. I appreciate that the site owner doesn't want this to turn into a selling thread, but wondered if you had any updates on the progress of these? I'm quite keen to get hold of one.

 

Cheers,

 

Kenny.

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The current situation is that we have completed our in house testing both on the bench and on the road. I have done 2000 miles on one of our units in my own car. Basically, we have gone as far as we can without getting some more assistance, so....

 

We are now gathering feedback from tuners / engine builders as an additional means of validating the units. in essence, we want to make sure that the timing curves are verified by independent means and that all the features function as expected. We have a unit going on an engine in a test cell next week If things go to plan.

 

This is a complex product when compared to out fuse panels. We want to make absolutely sure it is right before releasing it.

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Good to know. I'll be putting my own engine in my car in the coming weeks. It's an ex-3.0 SC that has had a brand new 98mm Max Moritz Mahle kit with John Dougherty 993SS cams and a full rework internally. As such I'm going to need to do some dyno runs to ensure it's not going lean at point in the range.

 

CIS should work fine with this set up and the fuelling shouldn't be too far out. Whilst the displacement is increasing to 3.2 the compression is also upped to 10.3:1 which should offset this somewhat. I'm hoping for 240bhp, but with your CDI unit and some tweaking I have a chance of taking that over 250bhp.

 

If you have a prototype you want to sell I'd be happy to test it out and report back.

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Nice ^^^^^^ :ani_clapping:

 

Very interested to see what it makes. Torque curve will be the most interesting with the MM kit.

Edited by GaryH
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