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the bypass is only really used until the thermostat opens. just gives somewhere for coolant pushed by the WP somewhere to go.
most engines i've seen that have an external bypass have about a 5/8" ID hose so it doesn't have to be a ton of flow.
typically when the T-stat opens the bypass ports get closed anyways, at least on 944/subaru/GM stuff i've messed with.
the bypass is only really used until the thermostat opens. just gives somewhere for coolant pushed by the WP somewhere to go.
most engines i've seen that have an external bypass have about a 5/8" ID hose so it doesn't have to be a ton of flow.
typically when the T-stat opens the bypass ports get closed anyways, at least on 944/subaru/GM stuff i've messed with.
The problem is that there is no coolant flow through the back of the cylinder head with the thermostat and heater core closed, this creates a large hot spot. I was hoping the turbo cooling loop would open the thermostat before that was a problem....oh well.
You nailed it, it was easier to just retain the cable rather than fab a new pedal, at least in my mind. It was kind of an early decision that I just stuck with. I was originally planning to run a normal 2 wire idle control valve as I didn't know the VR6 throttle body had it built in. I thought it was kind of cool that it's hybrid, cable driven but DBW style idle control. Ultimately though DBW is superior and the way to go. A number of VW/Audi DBW throttle bodies bolt right up, not difficult to find at all. I believe the stock 07K DBW throttle body bolts up.
Here is some cell phone video with a bit of revs. This is a very rough tune. I'll get some better video once it's actually driving.
So I tried the 4-port heater control valve but had to install the hoses opposite of the "proper" flow to get it to fit how I wanted. It didn't work.... if you look at how the valve works it really shouldn't have made a difference but I couldn't get it to flow, so the little arrow designating flow direction matters. One thing I don't like about this valve is that the diverter inside doesn't create a seal, it is just that, a diverter. To get this valve to fit how I wanted was too much of a pain in the ***, so I ditched it.
Here is the setup I went with. It utilizes the 944 3/4 normally open valve and a 5/8 normally closed valve. The 3/4 valve I got from 928 Motorsports a long time ago, I believe it is a UAC HV1020. The 5/8 valve is a UAC HV1021C. The vacuum feed is teed between the valves and when one is open the other is closed. Coolant can either flow through the heater core or through the bypass. The heater core return is through the o-ring port on the thermostat housing and the bypass is to the lower 3/4 barb on the thermostat housing. These valves create a positive seal and don't allow any coolant to flow when closed. So far it seems to be working great. It was overheating a bit at first but I think I had some air in the system as it hasn't done it again.
I have an autocross event next month where I will try and get some video. Here is everything I can think of so far.
The cooling system works great but is a massive pain in the *** to bleed the air out. Once all the air is out, no issues.
Even with a variable speed fuel pump I overheated it with a quarter tank of fuel. Fuel temperature hit about 100 °F in light traffic and it started to go out. Once it cooled down it was fine but still makes me a little uneasy. Not sure if there is a problem with the pump but I have a Bosch 200(044 replacement) on order just in case.
I will eventually migrate to drive-by-wire for more flexibility and better idle control, next winter project. In the Link ECU there is a 5% TPS lockout for the idle control so the current control method isn't ideal on cold starts where more than 5% throttle is needed. Once warmed up though I haven't really had any issues.
The SPEC Stage 3+ clutch feels pretty good. It makes a grinding noise when warmed up that seems to be going away as it breaks in, not really sure what's going on there or if that is normal.
I am still dialing in the tune but so far the car feels great on wastegate pressure, about 13 PSI. Low end power isn't even comparable to the stock 944 engine, VVT makes it even better.
The iABED valve/head cover I think could use a redesign on how it seals. There is a groove cut for an o-ring but it doesn't align with a few spots so is kind of useless. The best way to seal it is to use RTV but this makes it hard to remove. I would recommend cutting a groove for the OEM gasket. @Issam Abed
Here are some runs from the autocross. The car ran great with the exception of the fuel overheating on my way home causing the pump to barely work. The clutch still sounds weird but seems to hold power just fine. I did figure out that I needed a clutch pedal stop as I noticed I was overextending it, hopefully I didn't damage anything. I think some suspension upgrades are in order now.
I charged the A/C up and it works great. It definitely pulls a big alternator load so not ideal for sitting in traffic. Cruising you can't even tell and it is quiet as well. Funny enough, I noticed on a picture of an LMP2 race car that they use the exact same compressor or variant of it for some sort of cooling.
I did replace the fuel pump with a Bosch 0 580 464 200 as the Fuelab was getting worse. Not sure if I was just choking it with the small fuel lines or what, the variable speed was suppose to alleviate that though... I might sent it back to Fuelab and have them look at it.
Lastly, something is wrong with the clutch. It locked up on me today cruising around town but then seem to free up again. I am going to pull the torque tube and bellhousing and see what's going on.
I charged the A/C up and it works great. It definitely pulls a big alternator load so not ideal for sitting in traffic. Cruising you can't even tell and it is quiet as well. Funny enough, I noticed on a picture of an LMP2 race car that they use the exact same compressor or variant of it for some sort of cooling.
I did replace the fuel pump with a Bosch 0 580 464 200 as the Fuelab was getting worse. Not sure if I was just choking it with the small fuel lines or what, the variable speed was suppose to alleviate that though... I might sent it back to Fuelab and have them look at it.
Lastly, something is wrong with the clutch. It locked up on me today cruising around town but then seem to free up again. I am going to pull the torque tube and bellhousing and see what's going on.
Did you ever get to the bottom of the clutch and Fuel Lab issues?
Did you ever get to the bottom of the clutch and Fuel Lab issues?
I haven't had a chance to look at the clutch yet as I have been busy with other things. Planning to dedicate some time to it before Spring and will update here as soon as I figure it out.
The Fuelab issue was definitely pump cavitation(https://www.fuelab.com/blog/what-is-...to-avoid-it/76 ). I don't have a definite answer as to why though. Could be a crappy pump, being oversized(although variable speed was suppose to prevent this), more insulation needed on engine bay fuel lines, factory pump inlet size, a combination of all these....who knows. We will see how the Bosch does.
Any idea what the electric compressor pulls amp wise? How large (amps) did you go with on your alternator? Who makes the compressor? Sounds like a way to eliminate one more hassle on the front of a standard engine. Great work! Keep it up!
Any idea what the electric compressor pulls amp wise? How large (amps) did you go with on your alternator? Who makes the compressor? Sounds like a way to eliminate one more hassle on the front of a standard engine. Great work! Keep it up!
I measured it at one time but don't remember exactly what it was pulling, under 60 amps I believe. It has three speeds so you can vary it a little. I am using a stock 140 amp alternator and didn't have any charging issues during the summer.
They are all made in China by a company called Benling. They sell them labeled and unlabeled which companies then sell as their own(i.e. Rencool MD18). https://www.classicretrofit.com/en-u...essor-ecu-only - This UK company uses the same one with a fancy PWM controller.
These should be the correct part numbers:
DM18A7-A0115X - 18CC - 12V - PWM Control
DM18A7-A0128X - 18CC - 12V - Manual 3 Speed Control
Sourcing one in the US was a pain as any company that labeled it as their own obviously marks the price way up. I was able to order a single one from here: https://www.acparts.cn/product/ac-100-1161/ It was around $550 shipped 3 years ago, could be more or less now. Kind of a sketchy ordering process but didn't have any issues. Super nice people with a little bit of a language barrier.
01-14-2022, 08:38 AM
