Intake air temperature
07-30-2014, 12:43 PM
#31
Instructor
Thread Starter
In the meantime I did some more tests. At the moment I am interested in normal driving conditions and since I was not sure how accurately my resistor measured the real air temps, I reverted to measuring the intake manifold temperature to see how much this affects the max ignition advance before knocking is detected.
At the typical low and mid rpm levels of the auto trans cars, it is possible to set about 5 degrees more advance with the intake manifold at 30degC as compared to 60 C (which is the saturation temperature after about 1 hour driving on normal roads). As one could expect, this translates into a noticeable difference in throttle response.
Now I am looking for a way to cool / keep the heat off the intake manifold without too much cutting of sheetmetal.
_____
Kurt
90 S4 satin black metallic
928 OC Charter Member
At the typical low and mid rpm levels of the auto trans cars, it is possible to set about 5 degrees more advance with the intake manifold at 30degC as compared to 60 C (which is the saturation temperature after about 1 hour driving on normal roads). As one could expect, this translates into a noticeable difference in throttle response.
Now I am looking for a way to cool / keep the heat off the intake manifold without too much cutting of sheetmetal.
_____
Kurt
90 S4 satin black metallic
928 OC Charter Member
08-02-2014, 01:40 PM
#32
Drifting
Kurt,
During my errands today i shot video of the wind tells i affixed to the leading edge of my vents. (i know you don't want to cut) But for others..
The hood vents placed where they are on my hood are definitely Not sucking in but rather allowing hot air to escape. I used a very light yarn tell and a heavier ribbon material.
Note:
There is virtually no wind today.
And I do not have a belt driven fan. The electric fan did not kick on until the shark was parked for a few moments as i took the last video.
During my errands today i shot video of the wind tells i affixed to the leading edge of my vents. (i know you don't want to cut) But for others..
The hood vents placed where they are on my hood are definitely Not sucking in but rather allowing hot air to escape. I used a very light yarn tell and a heavier ribbon material.
Note:
There is virtually no wind today.
And I do not have a belt driven fan. The electric fan did not kick on until the shark was parked for a few moments as i took the last video.
08-02-2014, 02:12 PM
#33
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Matt - I thought yours were far enough forward to vent, good proof. Shorter yarn would probably be better though (less weight & less multi-slat effects - it might stand up more perhaps).
I do think the optimum vent positioning is likely still ahead of yours - probably just ahead of the wheel centers - has anyone done that?
In the end the intake will still heat substantially in stop & go at ~idle - not sure if this will reduce running temps much... any tests?
Alan
I do think the optimum vent positioning is likely still ahead of yours - probably just ahead of the wheel centers - has anyone done that?
In the end the intake will still heat substantially in stop & go at ~idle - not sure if this will reduce running temps much... any tests?
Alan
08-02-2014, 02:38 PM
#34
Drifting
Yes i routinely took temp readings in the same locations with the same IR device i keep in the car. I did this because my Temp gauge has had a mind of its own since i bought the car. So i was taking temps for a year prior to all the mods..
I have noticed lower readings now that there is venting and less weight and 1 accessory belt. How much affect the vents alone have made is anyone's guess. But the car does seem to run cooler.
Recently readings in the high 160s F (IIRC 167F) from the water bridge,
i do not recall a reading in the 160s fully warmed up during Summer.
It was always in the 170s and low 180s F.
But this is from recent memory and I will have to get some numbers.
I did think the same about using shorter yarn and should have taped them in with the longer bits.
I am at about 17" on center of the vents,
from the rear edge of the hood. Still an obvious low pressure area.
I didn't put them more toward the front because I was worried about possible rain water entering the intake tubes if i were to get caught out
and i thought it was also a nice touch to see the 'spider' through the vents which is visible in the right daylight.
I should affix yarn before and after my vent location to test the
pressure data on the charts previously posted.
Take care Alan and thank you for all your help
I have noticed lower readings now that there is venting and less weight and 1 accessory belt. How much affect the vents alone have made is anyone's guess. But the car does seem to run cooler.
Recently readings in the high 160s F (IIRC 167F) from the water bridge,
i do not recall a reading in the 160s fully warmed up during Summer.
It was always in the 170s and low 180s F.
But this is from recent memory and I will have to get some numbers.
I did think the same about using shorter yarn and should have taped them in with the longer bits.
I am at about 17" on center of the vents,
from the rear edge of the hood. Still an obvious low pressure area.
I didn't put them more toward the front because I was worried about possible rain water entering the intake tubes if i were to get caught out
and i thought it was also a nice touch to see the 'spider' through the vents which is visible in the right daylight.
I should affix yarn before and after my vent location to test the
pressure data on the charts previously posted.
Take care Alan and thank you for all your help
08-02-2014, 03:25 PM
#35
Matt - I thought yours were far enough forward to vent, good proof. Shorter yarn would probably be better though (less weight & less multi-slat effects - it might stand up more perhaps).
I do think the optimum vent positioning is likely still ahead of yours - probably just ahead of the wheel centers - has anyone done that?
In the end the intake will still heat substantially in stop & go at ~idle - not sure if this will reduce running temps much... any tests?
Alan
I do think the optimum vent positioning is likely still ahead of yours - probably just ahead of the wheel centers - has anyone done that?
In the end the intake will still heat substantially in stop & go at ~idle - not sure if this will reduce running temps much... any tests?
Alan
08-02-2014, 04:04 PM
#37
Customers car.
The vents are off a Ford GT500 I believe. Looked for a few weeks at every option and I still can't find one I want for my car. We installed a 12" Spal as a pusher that is activated when the AC is turned on and have thought about adding a controller but at this point it's not necessary.
The lights are those Truck/Jeep lights you see everywhere now, coming up on two years with these installed and they still work fantastic. If they came in an 8" I'd have them on mine. They are 7's with painted OB trim rings.
The vents are off a Ford GT500 I believe. Looked for a few weeks at every option and I still can't find one I want for my car. We installed a 12" Spal as a pusher that is activated when the AC is turned on and have thought about adding a controller but at this point it's not necessary.
The lights are those Truck/Jeep lights you see everywhere now, coming up on two years with these installed and they still work fantastic. If they came in an 8" I'd have them on mine. They are 7's with painted OB trim rings.
08-02-2014, 06:07 PM
#38
Rennlist Member
this is the best place, based on the physical obstructions in the engine bay, and the lowest pressure zone.
although the pressure zone goes further to the windshield than i remember it, (based on the graphs) yours should work.
although the pressure zone goes further to the windshield than i remember it, (based on the graphs) yours should work.
08-02-2014, 06:19 PM
#39
It looks like we came up with the same spot for the same reason.
08-02-2014, 09:48 PM
#40
Drifting
Since we all know one another by now..
It's a beautiful car but i disagree on the vent design but not location.
(to me they don't fit.. they touch in the middle for no apparent reason which says the shape and size is not quite right
and vent is not intended for the car )
Also the lamps look odd the more i look at the car.
Like a person right out of eye surgery.
It's all EASILY reversible if the owner wants.
It is a beautiful car with great paint and wheels.
I know my 928 needs work still too.
Note To MK:
That's one nice looking race car.
And your simple straightforward hood vent shape/design looks good to my eyes but i would have radius'd the inside corners
to better compliment the 928 design. Look at the quarter windows and then your hood vent opening and you'll see what i mean.
08-03-2014, 08:17 AM
#41
Instructor
Thread Starter
Matt: interesting videos and clear indication of the flow direction. Your vents certainly do a good job.
Sean and Mark: interesting pics, I might do something similar. I am not so sure anymore that I can do without cutting. I am currently looking for a cheap used hood for destructive testing.
I did some more tests,too, the goal was to find out how much the hot air from the radiator heats the plenum.
First I wanted to know how hot the air actually is. I rigged a small plastic tube, facing forward with a temp sensor inside (not touching the tube). This assembly was mounted above the left valve covers between the plenum and the intake hose. A test drive showed what was to be expected: as soon as the thermostat opened, the air temp rose to around 70 C. Driving at higher loads/speed increased this to about 75 degC. Even when sitting in traffic, the temperature stayed in that range. My measurement setup may have been too slow to capture short blasts of hotter air may but overall my readings were pretty stable.
Next step was to see what happens if the hot air is kept off the plenum. I wrapped the plenum several layers of fabric: first a thick cotton towel, then one layer of aluminium foil and another layer of densely woven cotton cloth on top. The insulation was certainly not perfect but covered most of the exposed area and also blocked airflow underneath the plenum from the front. I expected to see lower temperature as the internal cooling by the intake air would take effect. With the temp sensor re-attached to the plenum I went for another drive.
The result quite clear: while cruising the plenum was heating up a little slower than without the insulation but the max temperature reached while driving ended up about the same.
However, when sitting in traffic the temps rose faster and higher than without the insulation. After shutting off the engine, the plenum heated up so much that the temperature switch was triggered and the fans came on again even though the hood was open.
So it appears that under my typical driving conditions, the heat from the radiator actually seems to stabilize the temperature of the plenum - even so at quite a high temperature of around 65degC.
So one way to proceed would be to block the flow of air around the plenum and venting it all through the hood. Then a cold air scoop would be needed, e.g. from the back of the hood, to provide extra cooling for the intake.
The risk is that one could end up with a cooler plenum but larger temperature fluctuations. Then a pefect EZK map tuning would still be impossible.
Sounds all rather complicated and lots of ways to make it worse then stock
More thinking required.
_____
Kurt
90 S4 satin black metallic
928 OC Charter Member
Sean and Mark: interesting pics, I might do something similar. I am not so sure anymore that I can do without cutting. I am currently looking for a cheap used hood for destructive testing.
I did some more tests,too, the goal was to find out how much the hot air from the radiator heats the plenum.
First I wanted to know how hot the air actually is. I rigged a small plastic tube, facing forward with a temp sensor inside (not touching the tube). This assembly was mounted above the left valve covers between the plenum and the intake hose. A test drive showed what was to be expected: as soon as the thermostat opened, the air temp rose to around 70 C. Driving at higher loads/speed increased this to about 75 degC. Even when sitting in traffic, the temperature stayed in that range. My measurement setup may have been too slow to capture short blasts of hotter air may but overall my readings were pretty stable.
Next step was to see what happens if the hot air is kept off the plenum. I wrapped the plenum several layers of fabric: first a thick cotton towel, then one layer of aluminium foil and another layer of densely woven cotton cloth on top. The insulation was certainly not perfect but covered most of the exposed area and also blocked airflow underneath the plenum from the front. I expected to see lower temperature as the internal cooling by the intake air would take effect. With the temp sensor re-attached to the plenum I went for another drive.
The result quite clear: while cruising the plenum was heating up a little slower than without the insulation but the max temperature reached while driving ended up about the same.
However, when sitting in traffic the temps rose faster and higher than without the insulation. After shutting off the engine, the plenum heated up so much that the temperature switch was triggered and the fans came on again even though the hood was open.
So it appears that under my typical driving conditions, the heat from the radiator actually seems to stabilize the temperature of the plenum - even so at quite a high temperature of around 65degC.
So one way to proceed would be to block the flow of air around the plenum and venting it all through the hood. Then a cold air scoop would be needed, e.g. from the back of the hood, to provide extra cooling for the intake.
The risk is that one could end up with a cooler plenum but larger temperature fluctuations. Then a pefect EZK map tuning would still be impossible.
Sounds all rather complicated and lots of ways to make it worse then stock
More thinking required.
_____
Kurt
90 S4 satin black metallic
928 OC Charter Member
08-03-2014, 11:23 AM
#42
Drifting
Kurt,
This is a fun topic for sure.
The more i think about vent placement the more i think I got it right placing mine as far back as i could and centered over the intake and motor.
This is the location in the very top cavity of the hood where hot air would
just linger. Without the hood insulation in place this cavity can be seen well.
It would seem logical that venting as high up in/on the sloping hood, but still within the low pressure zone would allow the most hot air to naturally and consistently escape easiest, regardless of the chart showing a slight increase of pressure from loc 8 to loc 9.
My vents were centered over location 9 on the chart below or directly over the spider and motor in my '83S.
I thought it looked better there as well being a front engine'd automobile.
As far as our factory air intake design is concerned,
I think it is a good one overall.
This is a fun topic for sure.
The more i think about vent placement the more i think I got it right placing mine as far back as i could and centered over the intake and motor.
This is the location in the very top cavity of the hood where hot air would
just linger. Without the hood insulation in place this cavity can be seen well.
It would seem logical that venting as high up in/on the sloping hood, but still within the low pressure zone would allow the most hot air to naturally and consistently escape easiest, regardless of the chart showing a slight increase of pressure from loc 8 to loc 9.
My vents were centered over location 9 on the chart below or directly over the spider and motor in my '83S.
I thought it looked better there as well being a front engine'd automobile.
As far as our factory air intake design is concerned,
I think it is a good one overall.
08-03-2014, 11:50 AM
#43
Instructor
Thread Starter
Matt
it definitely is fun and if I am lucky, I get my hands on a cheap hood today.
I think about just buying one of those Subaru impreza hood scoops which feed the intercooler (like this:www.ebay.de/itm//201136941652). At least they are known to work (if placed correctly).
It may look crap but this would be a quick and dirty way to test different settings and see if it works at all. It also would leave my pristine hood un-molested so that I can fit it back on when it turns out that all this mods create more problems then solving them...
_____
Kurt
90 S4 satin black metallic
928 OC Charter Member
it definitely is fun and if I am lucky, I get my hands on a cheap hood today.
I think about just buying one of those Subaru impreza hood scoops which feed the intercooler (like this:www.ebay.de/itm//201136941652). At least they are known to work (if placed correctly).
It may look crap but this would be a quick and dirty way to test different settings and see if it works at all. It also would leave my pristine hood un-molested so that I can fit it back on when it turns out that all this mods create more problems then solving them...
_____
Kurt
90 S4 satin black metallic
928 OC Charter Member
08-03-2014, 12:11 PM
#44
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
There is always some post rad airflow through & around the engine - it may be that venting can cool it better - especially if you can create a seperate dedicated cooler air path around the intake - as Kurt was taking about above. This requires diverting hot radiator air down & away too - not so easy.
Alan
08-03-2014, 12:15 PM
#45
Drifting
Sounds like a sound plan Kurt.
If you like old racing cars as much as i do you can see they vented front engined cars up high and behind the motor on their sloped hoods.
The LeMans winning ('55-'57) and revolutionary, D type Jaguar comes to mind.
Malcolm Sayer, who worked at Bristol Aeroplane Company during the Second World War was an aerodynamic bodywork specialist. He also did the later C types as well.
The pressures up front are probably very similar if not higher on the hood where he placed his vents, directly above and behind the motors and exhaust manifold in high pressure locations. Winning Lemans wasn't easier then.
When i make a change to my vent design ( i want an Arrow Blue 928 lightweight eventually) it would be to increase the size by shaping it as shown and pushing them outward to allow more exhaust manifold heat to escape freely.
If you like old racing cars as much as i do you can see they vented front engined cars up high and behind the motor on their sloped hoods.
The LeMans winning ('55-'57) and revolutionary, D type Jaguar comes to mind.
Malcolm Sayer, who worked at Bristol Aeroplane Company during the Second World War was an aerodynamic bodywork specialist. He also did the later C types as well.
The pressures up front are probably very similar if not higher on the hood where he placed his vents, directly above and behind the motors and exhaust manifold in high pressure locations. Winning Lemans wasn't easier then.
When i make a change to my vent design ( i want an Arrow Blue 928 lightweight eventually) it would be to increase the size by shaping it as shown and pushing them outward to allow more exhaust manifold heat to escape freely.