Knackered old Porsche with loads of natural light - Boxster!

[gofasterrosssco]

poppopbangbang said:

gofasterrosssco said:

Why stop there - at ~560mm long, my internet fag packet calcs suggest the 5.2L V10 would squeeze in there*

• - Minor massaging required

Chop the boot floor out and there would even be room for the gearbox!

Haha Quite! Could you please advise the length of your 1.8T engine (bell housing flange to end of crank pulley)? You seem to have a decent amount of space between the engine and bulkhead.

[poppopbangbang]

gofasterrosssco said:

Haha Quite! Could you please advise the length of your 1.8T engine (bell housing flange to end of crank pulley)? You seem to have a decent amount of space between the engine and bulkhead.

Definitely end of pulley on the 1.8T or to the mounting face of the front engine mount? The latter would give you the total available length with the box in the standard position as the bulkhead is pretty much inline with that.

Let me know and I'll get the measuring tape out. Some of what you see on the CAD is space claim waiting to be finalised so it's not quite that much but it's pretty significant!

[Superferret]

This is ace, exactly the sort of project I would like in my fantasy workshop. Have often thought about the cheap Porsche route, then thinking around the probability of the knackered engine and what interesting alternatives there could be. Keep up the good work sir!

[Escy]

I saw this thread early on, I've just caught up on it now and things have taken an interesting turn. I've also got an Audi powered Boxster.

Is all your CAD done with the gearbox in the original position or are you lowering it? The 1.8t's I've seen in a Boxster have problems with the height. I've seen lots of people start these swaps (mainly in the US), not sure I've seen a completed car though.

There is a guy in America (or maybe Canada) that is developing a K20 swap for a Cayman (he's on YouTube), he ended up going transverse mounted. It seems wrong but it made a lot of sense when you saw it from a packaging point of view.

I ran a Boxster 5 speed (with a Kaaz diff in it) at 400ft/lbs with no issues.

Some things that might be useful information. The later 986 (and 987) 5 speed gearbox has output flanges with larger bolts (up from M8 to M10) with larger driveshafts. The stock Boxster DBW pedal worked fine with the Audi ME7 ECU when I tried. The 987 engine cover is made from aluminium rather than composite like on the 986, it's lighter and has more engine clearance so a worthwhile swap.

[poppopbangbang]

I've seen yours and I like it a lot! When I was deciding what motor to go for on this project I re-read your thread. Top job doesn't quite do it justice!

Escy said:

Is all your CAD done with the gearbox in the original position or are you lowering it? The 1.8t's I've seen in a Boxster have problems with the height. I've seen lots of people start these swaps (mainly in the US), not sure I've seen a completed car though.

There's a couple of AEB ones in the US but very few 06A based ones if any. I've heard this height thing from someone else but don't really understand it as the crank centreline is the crank centre line, that's the only bit between engines that doesn't change . I was told "it ends up at an angle" but of course that can only happen if the front engine mount height is incorrect - either way it all fits on CAD and there's plenty of sump clearance so we'll see when it's in the car.

Escy said:

There is a guy in America (or maybe Canada) that is developing a K20 swap for a Cayman (he's on YouTube), he ended up going transverse mounted. It seems wrong but it made a lot of sense when you saw it from a packaging point of view.

I think this is a case of so concerned if he could he didn't stop to think if he should ..... K20 swaps are what Elise were built for after all

Escy said:

I ran a Boxster 5 speed (with a Kaaz diff in it) at 400ft/lbs with no issues.

Officially it's 420NM and I'm trying to stick to the OEM ratings for everything on this (hence an RS4 clutch etc.). I can make the power required inside of that rating albeit over the RPM limit for the box slightly when on the PTP but they're a tough old gearbox for sure!

Escy said:

Some things that might be useful information. The later 986 (and 987) 5 speed gearbox has output flanges with larger bolts (up from M8 to M10) with larger driveshafts.

Weirdly they're rated at the same torque though despite being heavier! It could have been a metallurgy change for cost down though or just no requirement to durability at anything higher but I can't find any info on that or who drew them originally or an actual reason for the change. The 996 was the same with gen 2 cars going to thicker rear shafts but again they were rated at the same torque.

Escy said:

The stock Boxster DBW pedal worked fine with the Audi ME7 ECU when I tried.

I've found it's the same Bosch pedal sensor on the 9X6 as on the S4 and a few other Audis (and 3.5L Formula Renault ) so should PNP. I am going to retain the original cable pedal and just mount the DBW pedal sensor in place of the 90 degree drive for the original throttle cable.

Escy said:

The 987 engine cover is made from aluminium rather than composite like on the 986, it's lighter and has more engine clearance so a worthwhile swap.

That's very useful, it needs +12MM at the rear to clear the rocker cover and that's an easier mod on an ally one! Thank you, very handy to know!

How has yours been with regards bay thermals? The surface temps are going to be pretty high on mine around the exhaust manifold, turbine housing, downpipe and cat - certainly WAY more than would ever have been tested originally in that area on account of how much more energy is kicking around on that side (370kW minus turbine vs 75kW originally ) so I'm super keen to try and get ahead of that issue. I'm hoping that given the significant increase in free space around that area it'll be pretty easy to get away with although free flow into the bay will be somewhat restricted as the air intake is on one side and the other side is being used to feed the charge cooler heat exchanger with the outflow into the bay so whilst the deltas will still be good vs the manifold surface temps it'll have an impact on flow.... still finding this out is all part of the fun right

Edited by poppopbangbang on Tuesday 19th September 23:47

[poppopbangbang]

Couple of big bits back today....





I'm not going to start building it until next month but I might put the crank in the block just as an excuse to measure up properly and to store the crank somewhere out the way

The block has gone to 81.5mm (so first oversize basically) and the head has had some new exhaust guides, seats recut and a very, very mild skim. The crank measured up within nominal tolerance so we're pretty good all round with the big bits!

[Escy]

poppopbangbang said:

There's a couple of AEB ones in the US but very few 06A based ones if any. I've heard this height thing from someone else but don't really understand it as the crank centreline is the crank centre line, that's the only bit between engines that doesn't change . I was told "it ends up at an angle" but of course that can only happen if the front engine mount height is incorrect - either way it all fits on CAD and there's plenty of sump clearance so we'll see when it's in the car.

How has yours been with regards bay thermals? The surface temps are going to be pretty high on mine around the exhaust manifold, turbine housing, downpipe and cat - certainly WAY more than would ever have been tested originally in that area on account of how much more energy is kicking around on that side (370kW minus turbine vs 75kW originally ) so I'm super keen to try and get ahead of that issue. I'm hoping that given the significant increase in free space around that area it'll be pretty easy to get away with although free flow into the bay will be somewhat restricted as the air intake is on one side and the other side is being used to feed the charge cooler heat exchanger with the outflow into the bay so whilst the deltas will still be good vs the manifold surface temps it'll have an impact on flow.... still finding this out is all part of the fun right

With my engine (which isn't as tall as yours?) I couldn't have the crank centreline in the same place as the Porsche engine was, it would sit way too high so I had to lower the engine. I then lowered the gearbox to try and balance it out.

There's a nice thread here with a 2.7t swapped Boxster in the US. https://www.audizine.com/forum/showthread.php/9395...

Like me, he also had to mount the gearbox a bit lower in the chassis. If the CAD is saying it's not a problem I'm interested to see how you get on when you put it in the hole.

Heat management and airflow are the biggest hurdle. Most mid engine cars have a lot more ventilation than we do. If I used mine on track I'd have been tempted to get the angle grinder out. I've got the OEM fan on one side which I have set-up to run when the car is stationary or under 10mph and the other side is open. I'm not totally convinced the side ducts actually draw much air in when the car is moving. If your whole charge cooler system sits inside the engine compartment I think it'll heat soak fairly quickly (I know that's how Porsche have done the turbocharged Boxster's/Cayman's).

My charge cooler system isn't brilliant, from the data I collect it all seems like it's working correctly but it can't cope with a decent pull at high boost, it gets overwhelmed towards the top of the rev range. Possibly the Mercedes charge coolers I use aren't a big enough surface area, maybe the coolant flow rate isn't fast enough. I guess you've got good experience with these systems so you'll probably do a better job but I feel like developing an effective charge cooler system is a massive project in it's own right. I got mine to a reasonable level, (I can have it on a lower boost and it'll do alright) and then added WMI which is like a cheat code. The car can sit on the dyno all day long and the IAT's are decent still.

The reason I mentioned the K20 swap wasn't because of the engine choice, more the options that seemed to open up when fitting a 4 banger engine in a transverse layout. It was an eye opener as it wouldn't have crossed my mind to mount one like that if I hadn't seen it. It would leave lots of space where the old gearbox used to be (for an air to air intercooler). https://www.youtube.com/watch?v=CqWXAURiyfw

[gofasterrosssco]

poppopbangbang said:

gofasterrosssco said:

Haha Quite! Could you please advise the length of your 1.8T engine (bell housing flange to end of crank pulley)? You seem to have a decent amount of space between the engine and bulkhead.

Definitely end of pulley on the 1.8T or to the mounting face of the front engine mount? The latter would give you the total available length with the box in the standard position as the bulkhead is pretty much inline with that.

Let me know and I'll get the measuring tape out. Some of what you see on the CAD is space claim waiting to be finalised so it's not quite that much but it's pretty significant!

Well the front engine mount to gearbox bell housing position would be the preferred measurement I just presumed the engine dims would be an easier one as you have the scan / model in front of you.. Also, looks like the bulkhead tapers up near the top? Not and issue for a flat engine, of course. Thanks

[ATM]

poppopbangbang said:

As a package check I'd probably order a cheap joint from McGill and mock it up with a bolt and washers

My cheap joint has arrived - first thoughts are damn its stiff

[poppopbangbang]

Escy said:

With my engine (which isn't as tall as yours?) I couldn't have the crank centreline in the same place as the Porsche engine was, it would sit way too high so I had to lower the engine. I then lowered the gearbox to try and balance it out.

There's a nice thread here with a 2.7t swapped Boxster in the US. https://www.audizine.com/forum/showthread.php/9395...

Like me, he also had to mount the gearbox a bit lower in the chassis. If the CAD is saying it's not a problem I'm interested to see how you get on when you put it in the hole.

Interesting! On my CAD it looks like the rocker cover is essentially out the top of the bay but not by so much than the standard cover with +12MM across the back side wouldn't clear. It's close on the front edge/front of rocker cover to cover flange but not quite a clash. There's also the option of making a short rocker cover that dispenses with the seperators etc. in the standard one which I did for a previous motorsport project with this engine - again for clearance.

Escy said:

Heat management and airflow are the biggest hurdle. Most mid engine cars have a lot more ventilation than we do. If I used mine on track I'd have been tempted to get the angle grinder out. I've got the OEM fan on one side which I have set-up to run when the car is stationary or under 10mph and the other side is open. I'm not totally convinced the side ducts actually draw much air in when the car is moving. If your whole charge cooler system sits inside the engine compartment I think it'll heat soak fairly quickly (I know that's how Porsche have done the turbocharged Boxster's/Cayman's).

My charge cooler system isn't brilliant, from the data I collect it all seems like it's working correctly but it can't cope with a decent pull at high boost, it gets overwhelmed towards the top of the rev range. Possibly the Mercedes charge coolers I use aren't a big enough surface area, maybe the coolant flow rate isn't fast enough. I guess you've got good experience with these systems so you'll probably do a better job but I feel like developing an effective charge cooler system is a massive project in it's own right. I got mine to a reasonable level, (I can have it on a lower boost and it'll do alright) and then added WMI which is like a cheat code. The car can sit on the dyno all day long and the IAT's are decent still.

You're right in that water/air heat exchangers have the potential to be a pretty deep project! When you consider it's the interaction of two thermal systems then it does make sense that it would be. I've done some work in this area previously and some recently on their use in cooling intake air in an electrically boosted H2 fuel cell system but there's still a lot of considerations that I've never gotten near. The key elements though are:

- Heat exchange between the intake air mass and the coolant in the intake air heat exchanger core.
- The rate of thermal transport from the heat exchanger core
- The total amount of thermal mass in the system.
- Heat exchange between the coolant and the ambient air via the coolant system heat exchanger.

Everything becomes easier with more thermal mass in the system as that in turn reduces the rate at which you need to lose thermal to atmosphere given a fixed period of thermal addition to the system / duty cycle but then this only works if the intake air heat exchanger is capable of the level of heat exchange required to keep the air mass in the desired window in the first place. Supporting longer runs / periods of thermal addition to the system is really a case of increasing the rate of exchange to atmosphere and/or the amount of thermal mass in the system.... the flow calculation for optimium circulation is pretty easy then assuming the drops of both heat exchangers are known.

Basically it's two lots of Q=c∗p∗F∗Δ T flying in close formation with a set of flow rate calculations between...... or you just nail the largest core you possibly can in there, try to give it access to as much thermal mass as possible and then see where you end up

If you want to easilly test if it is the core or the coolant side of the system that is the problem and assuming there's a drain near your dyno it's entirely possible to plumb the charge cooler core to mains water and total loss it down the drain - that will give you infinite thermal mass at a decent flow rate so you can test the core performance in isolation.

[poppopbangbang]

ATM said:

My cheap joint has arrived - first thoughts are damn its stiff

New ones always are, the problem is the cheap ones go loose and floppy way sooner than the expensive ones

[braddo]

Watching with interest and enjoying the info sharing with Escy

[braddo]

On the heat extraction, might a solution be something like the inverse of a 992 GT3 bonnet? A duct on either side of the engine bay going through the rear firewall/bulkhead and up out of vents on the bootlid?

Obvs not an OEM look but a quick look at google images suggests there isn't an obvious path for lots of heat to escape the engine bay?

[poppopbangbang]

braddo said:

On the heat extraction, might a solution be something like the inverse of a 992 GT3 bonnet? A duct on either side of the engine bay going through the rear firewall/bulkhead and up out of vents on the bootlid?

Obvs not an OEM look but a quick look at google images suggests there isn't an obvious path for lots of heat to escape the engine bay?

That is one option but any modification to the bulkheads / shell equals an immediate IVA requirement as it fails the DVLA radically modified vehicle test - one of the main targets for this is that it stays on the right side of all things DVLA and vehicle registration!

I think extraction is okay as it falls out the bottom of the car quite effectively but getting it in is the hard bit

[ATM]

[braddo]

Or....

[poppopbangbang]

braddo said:

Or....

That would definitely be a statement! Could do it as a hard top so it dropped on for track days

[Dr.Hellno]

Function over fashion

Happy seeing this progress!

[ATM]

poppopbangbang said:

ATM said:

My cheap joint has arrived - first thoughts are damn its stiff

New ones always are, the problem is the cheap ones go loose and floppy way sooner than the expensive ones

[skwdenyer]

poppopbangbang said:

You're right in that water/air heat exchangers have the potential to be a pretty deep project! When you consider it's the interaction of two thermal systems then it does make sense that it would be. I've done some work in this area previously and some recently on their use in cooling intake air in an electrically boosted H2 fuel cell system but there's still a lot of considerations that I've never gotten near. The key elements though are:

- Heat exchange between the intake air mass and the coolant in the intake air heat exchanger core.
- The rate of thermal transport from the heat exchanger core
- The total amount of thermal mass in the system.
- Heat exchange between the coolant and the ambient air via the coolant system heat exchanger.

Everything becomes easier with more thermal mass in the system as that in turn reduces the rate at which you need to lose thermal to atmosphere given a fixed period of thermal addition to the system / duty cycle but then this only works if the intake air heat exchanger is capable of the level of heat exchange required to keep the air mass in the desired window in the first place. Supporting longer runs / periods of thermal addition to the system is really a case of increasing the rate of exchange to atmosphere and/or the amount of thermal mass in the system.... the flow calculation for optimium circulation is pretty easy then assuming the drops of both heat exchangers are known.

Basically it's two lots of Q=c?p?F?? T flying in close formation with a set of flow rate calculations between...... or you just nail the largest core you possibly can in there, try to give it access to as much thermal mass as possible and then see where you end up

If you want to easilly test if it is the core or the coolant side of the system that is the problem and assuming there's a drain near your dyno it's entirely possible to plumb the charge cooler core to mains water and total loss it down the drain - that will give you infinite thermal mass at a decent flow rate so you can test the core performance in isolation.

The next step is to get freon in the loop to cool the water in the charge cooler circuit