Slightly O/T - 996 rebuild / Boxster transplant

[rhd racer]

I couldn’t take any pictures at the time due to my broken phone, but after much swearing and discounting g glueing the sensor in or taking the engine apart and splitting the cases I came up with a plan.

That being to make a tiny relief in the case, insert the sensor then rotate clockwise 10-15 degrees to allow a new hole to be drilled in the case next to the one with the snapped tap on it. By Jove it worked



You can see the old tap stuck in the case next to the new M6 threaded hole. We live to see another day


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[rhd racer]

Next up is working out the fuelling system. Fuel rails first, the 996 rails and pipes obviously fit the application but create a couple of problems

1. The ones I had, though not obvious at the time, were from a 996 gen 2, so later than my actual engine. These were donated by Gus because we had a feeling my 2.6 rails would not work. The Gen 2 ones, it turns out, are a closed loop arrangement with no return to the tank, whereas my existing set up was open loop with a return

The pics below show my 2.7 ones attached to the old inlet manifold, and my older still 2.5 arrangement. Neither fit the 996 manifolds on mounting spacing or depth. The second pic shows the outlet for the return




2. The 996 ones route in a way which is not helpful if you turn the engine round the other way. On the plus side, you can fit them backwards, but that means you have a Y split in the main fuel line by the alternator which I think would be problematic with the belts, or if you fitted them as they are in a 996 the split is by the throttle body (the tightest part of the whole conversion) and you would need to run a line underneath the inlet and onto of the block in some way. I wasn’t really keen on this from a heat point of view

Here is a pic of the first of those not very good options



It just wasn’t right, and was also difficult to connect to the main feed line without linking the hose. Here it is off the car



Then whilst doing my research I found another factory routing for the fuel pipes up the near side front of the engine. Bizarrely this is also a 2.5 so open loop, but different to my 2.5 set up. It splits the left and right bank feeds in a much more sensible place, so I bought a second hand unit



This is the bit I will use



So I fitted the rails backwards and test fitted an injector to make sure it seated properly and it did - so plan hatched




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[rhd racer]

With a fuel rail solution, a pipe routing plan I then needed to get my head around the return.

The open loop system uses a vacuum fed pressure regulator pictured - this is not present on the 996 fuel rails



I read that you can simply change the fuel pump and sender unit in the tank at the front, to convert from one to the other. All the pumps are the same bar this difference, so an early 986 pump (even a 2.5) is the same as a 996 3.4. I could not find any Gen 1 rails for sale anywhere, so bought a good used 987S pump from c2005, which is the same as a Gen 2 996 pump. I haven’t fitted yet, but I will leave the return line in, just in case I revert at any point to the 2.7.

I then needed to check the injectors are compatible. I had invested in a new set of 3.4 996 injectors matched to the engine as I thought they are one of those parts that no one ever changes and they would optimise performance from what I had. Having moved to a later closed loop pressure system though, these are no longer right for the fuel system. A quick call to Wayne Schofield and he confirmed they would be ok, he will just need to flash the ECU with pressure values for each one. On the open loop system, the vacuum regulator first mechanically and the ECU has values of 1 for each injector.



The old 2.7 injector on the left is the newer design, but Wayne said they do not seat as easily as the old style ones so I am sticking with the original spec 3.4 ones.

So, I rust treated and sprayed the 996 rails knowing I had a solution to it all, even if none of it is built up yet. I will need to find some large diameter high pressure fuel hose to make up the connections between left and right banks. The rails seem to have massive barbed connections so this should all be pretty straight forward




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[rhd racer]

I’ve been kept away from the garage by a few days away over half term and an interesting bout of sickness I would rather forget. Anyhow, today I seized the carrot and got a good half day in having worked it all out in my head.

Firstly I put the crank position sensor in, secured by its new non OG fixing position with a longer bolt to ensure security, then refitted the flywheel again, this time with the clutch



Then moving to the fuel rail / pipe solution I knew which bits I was going to use so set about separating them from the old pipes. The old fuel lines are hard plastic, and covered with a rubber outer, so when kinked the inner can sustain damage you can’t see but could restrict fuel flow. One of the pipes I ordered for a fitting was rammed in the box and linked in such a way so that set a tone of replacing everything from the connector on the rear bulkhead to the fuel rails. The issue I knew I would face into is that connector is plastic and would be really difficult to fit.

Deferring that for a bit, I started with the easier splitter between left and right banks. I measured the pipe it came with to the fuel rail so it located in the factory position. It is basically a Y connector but allows for the pipes to ran next to each other

I struggled to get hold of fuel injection hose, but believe it or not Halfords came through with 9.5mm ID hose rated at 150psi, where the Boxster pressure is more like 55psi. The issue being that I had measured a 10mm ID plus barbs, so I knew it would be as tight as a gnats chuff. My plan was to use fuel sealing paste as a lubricant and sealer, as an insurance policy in all the joints. It is really good stuff, gets everywhere, but seals fuel joints like nothing else



You can see the exposed plastic inner pipe in the above. Below is the plastic elbow removed



Joint by joint, clamped in the bench, the softened pipes (soaked in boiling water) were slowly fitted




Until I had a completed rail assembly



The plastic elbow was every bit the nightmare I thought it would be!


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[rhd racer]

The new injectors were a breeze to fit with PTFE spray (recommended by Angus) can’t believe how easy. I tried last time with fuel that evaporated so quickly you end up trying to wrestle them in dry




With the securing clips fitted could do the other bank




I fitted the original rubber bungs on the outside of the new fuel pipes which help secure them and stop them rubbing in body or engine




So just plugs, coil packs, the remaining loom, vacuum pipe for the brake servo and gearbox to go before fire in the hole!


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[KS]

Blimey! And I thought my engine on ITBs was complicated... Well done young man.

[Bruce M]

The plastic original tube is nylon / polymide. I did research on this previously when i was weighing up plastic or metal hard line. You heat the end until soft then ram onto the fittings. The nylon id is less than a equivalent rubber hose I understand. You can source replacement stuff. It very resilient & handles ethanol, so unsurprisingly the OEM pick.

The fittings are something like SAE2044 but also called “type 7.89” which relates to the OD of the metal barb male fittings for a nominal 8mm size. Very common & easy to source replacements.

Hopefully Halfords have got their act together on rubber hose. For a spell they were selling R6 hose which would last 6months with E10

Id suggest inspecting every 6 months. If it does need replacing Cohline 2240 is decent in my experience and stands up to ethanol. It’s available in 9.3mm ID size

[wadsworthi]

Fantastic work Wayne, looking forward to seeing it run.

As Bruce says Cohline is very good for fuel hose and available from a company at Holmfirth along with fittings if needed. Let me know if you want a link.

[rhd racer]

Cheers Ian.

Very helpful info, thanks Bruce. I will take a look and see what I can do before I fit it then. I was not entirely happy with the jubilees but believe it or not they are rated at between 100-200 psi, way more than the rating requirement of the job. Mikalor clamps are my go-to for higher pressure applications but they only do 17-19mm. I have ordered some in the hope that the hose has increased slightly with the barbed end in it (which it seems to have done). That might all be academic if I can get a more OE solution. Super helpful

Thanks for the encouragement Keith!


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[rhd racer]

Here is the label - it says ethanol safe however a bit of googling raises questions, to your point Bruce.

Hmmm


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[Bruce M]

Yup, jubilee clips are frowned upon as they can cut into the hose. However, i used a few because the nice mikalor items where a bit tight & I didn’t want to use crimp on clips. I think if you take some care & don’t gorilla them, they are safe enough. They are also a good price / quality if you use genuine “Jubilee” items.

[rhd racer]

On the balance of your advice Bruce I gave ordered a couple of mtrs if the Collins 2240 from Merlin. Doing the fuel rails in situ is possible but not a great deal of fun, and I would rather do it once and not worry about them slowly dissolving in the background.

Given it is all coming off again, I have ordered 10 Mikalors as an insurance policy but think will be too loose - the Cohline hose OD is nearly 1mm smaller than the Halfords hose. However have also ordered a full suit of those crimp up stainless fuel pipe clamps (these ones that are infuriating to remove!)



They will be neater in installation terms and do match better to the OD if the Cohline hose.

I need to do it all again mind, but better now than the potential outcomes.

Thanks again for the warning


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[Cortina]

Could you not use some "tape" round the OD of the hose where the clip goes , and thus make the OD "correct" , so the clips are a perfect fit (it's what I would do ...... not always a good idea !!)

[misteralz]

I was involved in a similar discussion on another forum recently about coolant hose spring clips being the work of the devil. They are if you're trying to remove them with a screwdriver, or tin snips, or an old credit card. Use the correct tool, however, and they're an absolute joy. The same goes for those fuel clips - there's a tool for them that looks like a crimp, and it's reversible for installation or removal.

[misteralz]

https://www.ebay.com/itm/294297689763

Like these. One way's on, other way's off.