Oil pressure relief, oil cooler, and accusump interaction Options

[Seabird]

Good morning everyone. I am in the process of upgrading my oil system. This is on my dedicated track 914. The upgrades include remote oil cooler, accusump, and CB Maxi oil pump.

In my research for installing the accusump it seems like there are two places that are recommended, in the cooler return line with a check valve and direct to the block. I did not want to use the sandwich plate adapter so I opted for the block option. Simpler with less seals to fail.

As I looked into the workings of the type IV oil system I found a potential problem with both these locations; the oil relief valve on the front of the engine. VW used this valve to bypass the cooler when the oil is thick. But this also means the cooler is bypassed when the oil pressure is high. Does the use of an oil accumulator negate the oil cooler system by maintaining oil pressure?

While on the straights the pump could potentially make 50-60 psi of oil pressure. (the 30mm pump that was in the engine produces those pressures much of a 20 min session) At those oil pressures the cooler will be bypassed based on what I know of the relief valve (bypassing cooler at 60psi, partially open at 35 psi, and sealed at 12psi). The accusump will also build up to that pressure. When I go to brakes and the revs drop the accusump will start pushing back and keep the pressure up till the differential is corrected. If I am back on to the next straight in that time then the pump starts building the pressure again.

Options:

1. Am I making a mountain out of a mole hill? Leave it alone.

2. Plug that relief valve so it stays closed and let the oil cooler thermostat bypass the oil when its cold. This is a pre 76 case so there is the secondary relief valve by cylinder 1. Might be able just to invert the piston so the bypass grove is below the bypass passages.

3. There is also the high pressure pistons sold by pelican parts and others. Does this just shift the bypass window to a higher pressure range?

I would love to hear people's thoughts on this.

Miguel

[Jetsetsurfshop]

I just might.

Though this should get its own OT topic I'll give a short blurb here. We finished 6th at Daytona, two of our drivers had never been on the track before, and one of our drivers developed a fever while driving his stint. Had it not been for two silly penalties we would have been in the hunt for 1st place (15 min worth of penalties at sub 2:30 laps makes up the 6 lap differential at the end.) GRRRR.

Not bad for a team and car's first race! We are quite ecstatic to say the least!

Also I got to meet the George, the PaintedMan; which was cool.

OT race report over.

Mean while back on the 914 front I am excited for Chris's new solution to the oil cooler bypass issue! A week and a half away from getting to test it! Man its going to be hot at Sebring too!

Regards,

Miguel

Spoke with Chris today about this prototype for a bit. I'll block off some space next to my trailer for you. I'm track support for my dad on Sunday and will be able to help you out too. Looking forward to checking out the new components. Are you getting there Saturday night or Sunday morning?
Shane

[Seabird]

Spoke with Chris today about this prototype for a bit. I'll block off some space next to my trailer for you. I'm track support for my dad on Sunday and will be able to help you out too. Looking forward to checking out the new components. Are you getting there Saturday night or Sunday morning?
Shane

Should be there Saturday by 5 or so.

Just finished the accusump tonight. Finishing the cooler install is next.

So much to do so little time. (IMG:style_emoticons/default/biggrin.gif)

Miguel

[Jetsetsurfshop]

Well, get on it!! (IMG:style_emoticons/default/smash.gif)
See you there.
(IMG:style_emoticons/default/driving.gif)
Shane

[Seabird]

Well, get on it!! (IMG:style_emoticons/default/smash.gif)
See you there.
(IMG:style_emoticons/default/driving.gif)
Shane

Cooler installed!

(IMG:http://www.914world.com/bbs2/uploads_offsite/dl.dropboxusercontent.com-16683-1401454348.1.jpg)

[ww914]

[/quote]

Cooler installed!

(IMG:http://www.914world.com/bbs2/uploads_offsite/dl.dropboxusercontent.com-16683-1401454348.1.jpg)
[/quote]

Miguel

Let us know how this works out for you. When I installed my Tangerine Racing street headers, it moved most of the plumbing to the drivers side. I thought this location would be perfect. When I didn't see much improvement, I realized that I was probably picking up a lot of engine heat from the impeller. I moved the cooler higher and added a NACA duct on the right side rocker panel. Not sure how effective that is yet, but Foley has used that position with positive results, he says.

[Seabird]

I have a feeling that all the talk about rear mounted coolers being inadequate has more to do with this cooler bypass circuit than anything else. Between accusumps and high pressure pumps I think most track type iv's have been shooting themselves in their proverbial feet.

Thanks to Chris we might have a solution on our hands here.

Next weekend will be a good test of this. We shall see (IMG:style_emoticons/default/biggrin.gif)

Miguel

[Jetsetsurfshop]

Hey Miguel,
What was you track temps at the last event?
Shane

[ThePaintedMan]

I think he said he didn't have an oil temp gauge installed before?

[Seabird]

The new vdo gauge and the old sender were a mis-match so I had no data. It was wicked hot though. Swapped the sender last night so we will have data this time.

[Jetsetsurfshop]

Hey Miguel,
Did you install a pull-thru fan? I wonder what will happen at idle? What will the oil temps do? (IMG:style_emoticons/default/confused24.gif)
Just a concern with eliminating the stock cooler. We will know soon enough...
Shane

[Seabird]

No puller fan. It's a race car, it should not have to idle too much once it gets up to temp.

Some racer friends came over last night and we got a bunch of the car buttoned up. Today after work another friend came over with his scales and we corner weighted the car. 2166 with my full figure in the drivers seat. 50.2% cross 51.8% rear. Pretty happy with those numbers. That's puts me pretty close, weight wise to where I need to be for HSR.

Went through the whole accusump priming routine. Filled up the oil sump. Added extra for the cooler and fird it up. I let it idle for 10 mins and it did not break 150. With some higher revs I was able to get the gauge to approach 170. Did that for a little while and gave up on getting it to heat up. The cooler was warm to the touch and the gauge was reading, works for me.

I still have a few details to sort out but the bulk of the work is done. Will be ready for next Sunday in no time (IMG:style_emoticons/default/biggrin.gif)

[ChrisFoley]

Hey Miguel,
Did you install a pull-thru fan? I wonder what will happen at idle? What will the oil temps do? (IMG:style_emoticons/default/confused24.gif)
Just a concern with eliminating the stock cooler. We will know soon enough...
Shane

The stock cooler doesn't work for shit at idle anyway.
A remote cooler will radiate more heat without air flowing thru it than the stock one does at 900 rpm engine speed.
A fan on the cooler will impede airflow when driving at high speeds.

[Jetsetsurfshop]

Hey Miguel,
Did you install a pull-thru fan? I wonder what will happen at idle? What will the oil temps do? (IMG:style_emoticons/default/confused24.gif)
Just a concern with eliminating the stock cooler. We will know soon enough...
Shane

The stock cooler doesn't work for shit at idle anyway.
A remote cooler will radiate more heat without air flowing thru it than the stock one does at 900 rpm engine speed.
A fan on the cooler will impede airflow when driving at high speeds.

Good to know about the stock cooler.
Plan on selling the factory oil cooler delete system yet? Don't see a price listed on the website.
Shane

[Bill's Racing 914]

(IMG:style_emoticons/default/biggrin.gif)

Good morning everyone. I am in the process of upgrading my oil system. This is on my dedicated track 914. The upgrades include remote oil cooler, accusump, and CB Maxi oil pump.

In my research for installing the accusump it seems like there are two places that are recommended, in the cooler return line with a check valve and direct to the block. I did not want to use the sandwich plate adapter so I opted for the block option. Simpler with less seals to fail.

As I looked into the workings of the type IV oil system I found a potential problem with both these locations; the oil relief valve on the front of the engine. VW used this valve to bypass the cooler when the oil is thick. But this also means the cooler is bypassed when the oil pressure is high. Does the use of an oil accumulator negate the oil cooler system by maintaining oil pressure?

While on the straights the pump could potentially make 50-60 psi of oil pressure. (the 30mm pump that was in the engine produces those pressures much of a 20 min session) At those oil pressures the cooler will be bypassed based on what I know of the relief valve (bypassing cooler at 60psi, partially open at 35 psi, and sealed at 12psi). The accusump will also build up to that pressure. When I go to brakes and the revs drop the accusump will start pushing back and keep the pressure up till the differential is corrected. If I am back on to the next straight in that time then the pump starts building the pressure again.

Options:

1. Am I making a mountain out of a mole hill? Leave it alone.

2. Plug that relief valve so it stays closed and let the oil cooler thermostat bypass the oil when its cold. This is a pre 76 case so there is the secondary relief valve by cylinder 1. Might be able just to invert the piston so the bypass grove is below the bypass passages.

3. There is also the high pressure pistons sold by pelican parts and others. Does this just shift the bypass window to a higher pressure range?

I would love to hear people's thoughts on this.

Miguel

Part of the problem could be from using the 40 year old check valve springs if you haven't already changed them out.

A spring will relax over time through thousands of heat cycles. I can only assume that an old spring now has the modulus of elasticity of silly putty.

In fact having a spring as part of a check valve for any high temp fluyid system is a bad idea anyway. The hotter the spring gets the looser it gets (the spring constant is a function of temperature). The only way to reduce this thermal effect is to get a spring made from inconel or titanium which will have flatter thermal response curves.

Plus buying a new sping may not be any better since it may have a lower modulus than an OEM spring.

The spring equation is very simple. Spring force = spring constant x deflection

You can check several springs aginst each other with a simple jig fixture where you can apply the same vertical load to each spring. The spring with the least deflection under the same load has the highest spring rate. The higher the spring rate, the higher the allowed cracking pressure...


Bill

[Seabird]

Bill, your words were prophetic!

Got to Sebring Saturday afternoon. Found Shane in the usual spot on the paddock. And began to unpack. Registration and Tech with Chin was a breeze. We were set for a nice day at the track. Little did we know there were gremlins laying in wait for us.

(IMG:http://www.914world.com/bbs2/uploads_offsite/dl.dropboxusercontent.com-16683-1402434139.1.jpg)

The long and short of temperatures was with the distraction of what was to come with oil pressures we got very little data on the cooling and the cooler bypass blank off kit. Between the rusty relief valve that was in the motor when purchased and a still unknown oil pressure issue I was not able to enjoy even half a session. We will try again in two weeks though so stay posted.

Sunday morning after the drivers meeting there was an open track warm up session which I was going to use to get in the grove before my evaluation session (first time running with Chin.) I could not even complete a warm up lap before my oil pressure dropped to the floor!!

As I idled in and through the pits pressure came back. 65-70 psi at idle. I thought maybe there was an air pocket in the cooler circuit and now its gone; head out and keep an eye on it. Nope, I got as far as Bishops Bend this time and the pressure disappeared. Idled in and hoped I did not do any serious damage.

A discussion among the friends on hand and we decided to check the pressure relief spring assembly. What we found was shocking to say the least.

(IMG:http://www.914world.com/bbs2/uploads_offsite/dl.dropboxusercontent.com-16683-1402434140.2.jpg)

Yep that is a rusty and scored piston and spring. If you have not inspected your oil pressure relief system in a while now is the time.

Our best guess of what was happening was that with the high oil pressures the engine was making the relief valve was fully extending and getting jammed open. A little jostling around and it would release. I had a new Weltmister high pressure kit on hand so that was swapped in. Ran a session with the fresh Weltmister piston and the rusty spring. Started to see ugly pressure drops after a few laps so I returned to the pits.

At this point we decided to test out the Foley blank off sleeve and piston. Very nice fit and finish. (I did not photograph it but I'll pull it out in the next day or two and post a picture here.) Ran a few more laps before the oil pressure light came on. At this point we were starting to suspect something else was causing the pressure drop off issue. The oil was hot but not hot enough to cause the massive pressure losses so soon.

For the four session we played around with some shrouding to block off hot exhaust wash from the headers entering the cooler. No significant change to oil temps. Pressure drop caused me to come in after 11 mins on track (IMG:style_emoticons/default/stromberg.gif)

Fifth and final session I decided to take it easy take a Sunday drive; it had not blown up yet might as well relax a bit and enjoy what was left of the day. More of the same. Got 16 mins in this time.

A big thanks to Shane and my friend Mike for coming out and lending a hand!! As usual Chris Foley's support and advice has been wonderful.

We have a few areas were I am going to look for the problems. Hopefully the gremlin will get sorted for the next track weekend. Stay tuned.

Miguel

[ChrisFoley]

This was my first time at the track with a completely new oiling system in 1997.



We drove 7 hours so I could hang out under the car all weekend. (IMG:style_emoticons/default/headbang.gif)
At least I had the sense to rent garage space in advance, so it wasn't unpleasant, just discouraging.

[Jetsetsurfshop]

I wish I could of been more help. Managing my Dad all day was a bigger challenge then I thought.
How did Warren's test go?
(pics of 914s in the paddock where they belong (IMG:style_emoticons/default/driving.gif) )

[Seabird]

Nice pic. Looks like we had a private test day at Sebring.

Miguel

[ww914]

I wish I could of been more help. Managing my Dad all day was a bigger challenge then I thought.
How did Warren's test go?
(pics of 914s in the paddock where they belong (IMG:style_emoticons/default/driving.gif) )

Not done testing yet. This last weekend was very hot, so I got some good baseline numbers. Installed the Foley valve yesterday, with the longer piston. (He sent me two) The outside air temp was pretty cool 55-60, so it took awhile to warm up. Once warm, I did not see a lot of difference in the numbers from testing with the old valve. I will put the shorter piston in tomorrow and see what happens. Playing golf today.

[ChrisFoley]

I wish I could of been more help. Managing my Dad all day was a bigger challenge then I thought.
How did Warren's test go?
(pics of 914s in the paddock where they belong (IMG:style_emoticons/default/driving.gif) )

Not done testing yet. This last weekend was very hot, so I got some good baseline numbers. Installed the Foley valve yesterday, with the longer piston. (He sent me two) The outside air temp was pretty cool 55-60, so it took awhile to warm up. Once warm, I did not see a lot of difference in the numbers from testing with the old valve. I will put the shorter piston in tomorrow and see what happens. Playing golf today.

I'm not certain yet but, based on my brief test, I think the shorter piston opens at a high enough pressure and the longer piston may be too much except for high revving engines.