Modified 944 turbo - taking in too much hot air?

[Masher]

At the Bedford track day, I noticed that on the main straight at the start of a session the car pulled like a train all the way. However, after a few laps, it was clear the car was not pulling as strongly and felt like something was restricting it. I don't suspect anything terminal since upon cooling, all was well again and this was repeated several times. I got chatting to one chap (sorry, new to 944's and so I don't know many of you so am at a loss for a name here) and he suggested the issue might be hot air being taken into the engine (presumably less oxygen to burn thus reducing power). Since the filter is located between the turbo and the intercooler (principally in line with the bonnet release catch) I can see that heat in this area could be an issue.

I noticed a couple of cars had air intakes taking the cone filter into the nearside wheel arch area behind he headlight. I'd like to try this but cannot find the required hose to make this happen - any ideas?

I'll try and upload a pic when I get onto my PC with the photos but I'd appreciate thoughts on the problem and proposed solution and also advice regarding where to get the tube necessary to take the cone filter into the area described which looks like a cooler haven to me.

The car is a modified 2.5L NA which is now a 2.8L Turbo and there is no air flow meter so I assume some electronics take care of that side of things (it has Motec electronics if that's a clue).

Thanks,
Mick

 

[T3rra]

Could help. However the Ic should have the final say on air temp going in to the intake. MIT be worth going 4 a stage 2 intercooler where the end tank is silghtly enlarge 2 aid flow.

Speak to Tom barks, he just got my intercooler modded.

Moving the the cone filter you could turn and cut the stock j boot bung the dump valve in let,

Get some universal alloy pipe with outlet 4 dump valve. You may need another bend.

But again, Tom got me a complete one peace pipe fab up.

 

[944Scott]

I have an intake fitted behind the front grills that fits straight in to the airbox intake pipe.

 

[T3rra]

Scott are you saying your using stock snorkel 2 draw cold air from inner wing ? To a cone filter in the same place? Or something else 2 duct ?

I don't think he has stock air box,

Most cone filters draw air from face not sure duct would draw air quite the same as air box.

 

[944 man]

Mines right behind the intercooler and I suspect that this would cause a real problem as everything got hot on track.

 

[T3rra]

Inverted cone could have ducting ran 2 it as it draw more, but will still taking in the hot air on the face.

This is my intention,



http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/598148-cold-air-intake.html

 

[924nutter]

Masher, I think it was 944 man who said in another thread, to Terry I think, who has chosen to go his own way and presumably cut the lift stop off the back of the headlight, that the standard turbo air filter is good for 320 bhp and it takes air in from the nearside wing. It may have been me you spoke to as I have been telling every one I speak to that I think a cone filter in the convenient place under the bonnet places it in warm ambient air, and probably negates what little advantage the wetted mesh filter confers. I took out the mesh filter that was in my 996T and now use the std paper filter which was what I was running at Bedford, having scraped through the noise limit at 101 db. I think I might even have come past you on the long staight once, I certainly overtook a riviera blue 944 before I melted my rear tyres.
Run your engine for a bit then open the bonnet and put your hand in there with the engine off. It feels warm, not a good place to suck air from.

 

[944 man]

Id swap back in a flash John, if I had a good airbox (and bypass valve too).

 

[TTM]

ORIGINAL: T3rra
However the Ic should have the final say on air temp going in to the intake.

Are you saying the IC can freshen inlet air below the temp of air going through the cone?

 

[T3rra]

I would expect he's putting out over 320 if its a 2.8ltr engine. Standalone ecu, I Don't know what set up he running.

Better flowing Ic could help. ( he may already have one )

From what I've read the only proven and tested filter set up is the one behind the head light, boxed in it own air box. Where drop below ambent where recorded, once a lid was on.

Iv not tested any off this myself, it just what Iv read and researched over the last few weeks, trying 2 figure out what I'm going 2 do with mine. Which Iv left the bump stop gone 4 a smaller filter.

 

[GPF]

ORIGINAL: T3rra
Where drop below ambent where recorded, once a lid was on.

If someone recorded lower temps than ambient there was something wrong with the way they recorded the temps.

 

[Masher]

Hope I manage to do this right... should be a pic of the current set up below.

I was not involved in building the engine so do not know exactly what components were used. I've plenty of invoices but some of them are not as detailed as you'd ideally like when it comes to discussions like this but I'll see what I can do. Showing my ignorance, what is an IC?

Looks to me the pipe from the header tank will be my main obstruction ref reversing the current intake pipe. With respect to a replacement these is clearly something (a vacuum tube?) coming off the intake which I guess would need to attach to any replacement part. As you can tell I'm not at the cutting edge of home mechanics! The car also has 924GT type headlights rather than the pop-up type - not sure if this provides more or less room?

The car is reported to be putting out 350BHP though comparing it to my 964 (250BHP) I suspect this may be true but it is a more peaky power output. The engine was built to take 450BHP on higher boost but then it needs a paddle clutch (that how you spell it?) which is like an on/off switch and I hated it (this was fitted when I bought the car and I immediately changed it).

Thanks for the thoughts,
Mick

 

[GPF]

Hi Mick,

The air filter is indeed in just about the worst location possible as it is will be taking in the hot air that exits through the back of the intercooler (IC).

The thing with the vac line will be your dump valve and will ideally need to remain plumbed in to any new intake piping.

By the way, re the paddle clutch - they don't have to be On/Off, it depends on the type.

My other car is a heavily modded Noble pushing out over 600bhp. That has a paddle clutch and it's very smooth to use and modulate.

 

[T3rra]

Nice power u got. Light conversion should give u more room as there no headlight frame for the pop ups. Stock air box won't help. So you can place a large air filter as near the hole in the wing as possable.

The hose your talking about I would assume is the J boot the dump valve is plumbed in to it from the panssangers side intercooler pipe.

You can use the Bend in the stock j boot and cut and rotate it then using bit off pipe and hoses make your way over to the head light area, you will need an outlet on one off bits off pipes to plumb the dump valve back in to if it been done like this already. Or do u get a noise when u change gear?

Ic is short for intercooler. Its under the badge pannle. If u can get it off take a look, see if one off the ends is smaller then the other, this is the end that gets enlarged.

 

[Masher]

There is a very noteable noise changing gear which will be the dump valve.

J Boot - thanks for the term. So much easier to google search when you know the name of the item. I'll have a play around and see what I can do and assess what mods I might need to make.

Any pitfalls to avoid whilst doing this?

The way the discussion is going I am assuming the consensus of opinion is that the symptoms I have described are related to hot air build up in the engine bay and this affecting performance on longer runs at full throttle?

I am also assuming that although I cannot see my own picture you can? I still don't get this showing pictures thing!

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Did I just do it....?

Cheers
Mick

 

[T3rra]

Maybe I'm mistaken or mislead. But by portioning off the cone filter in the engine bay it did prevent some heat soak.

Looks like your dump vavle is still pumped in for reculation, so I wonder if the noise your getting is though the cone?

 

[GPF]

ORIGINAL: Masher
The way the discussion is going I am assuming the consensus of opinion is that the symptoms I have described are related to hot air build up in the engine bay and this affecting performance on longer runs at full throttle?

It won't be helping, but whether it fully explains the drop off you describe may be another matter.

Although the headlight conversion has done away with the usual bracket, the back of the light unit itself now looks to be in the way which may explain why the filter was put where it is?

 

[Masher]

ORIGINAL: GPF

ORIGINAL: Masher
The way the discussion is going I am assuming the consensus of opinion is that the symptoms I have described are related to hot air build up in the engine bay and this affecting performance on longer runs at full throttle?

It won't be helping, but whether it fully explains the drop off you describe may be another matter.

Although the headlight conversion has done away with the usual bracket, the back of the light unit itself now looks to be in the way which may explain why the filter was put where it is?

That was my concern too. I'll have to have a play and see what is possible.

I could always poke the air filter through the damn great scoop they put in the bonnet [] (yes I am joking)
Mick

 

[T3rra]

Access will be tight, but u could put a small mushroom filter on the inside off the wing? Horns are on that side which could cause some obstruction but could work.

 

[924nutter]

Masher you have got rectangular lights haven't you? They dont pop up so. do a photo shop and flip the image horizonatally, in other words filp the cone through 180 horizontally and see what you need to position it right by the standard vent in the wing. Porsche put it there for a reason. T3rra's link to the pick that shows the infill panel to isolate the filter from under bonnet temperatures looks like something that would work for you as you have all the room in the world with out the pop up mechanism. Inducting cold air is very important to any engine, and if you ever get to see under the lid of some club one make racing series you will see that they take great pains to ensure that the inlet is fed with as cold an air-supply as they can engineer. A charge cooler. ( air/air or air water) does not increase the volume of air being sucked in. Your engine at 6000 rpm flows 300 cfm to all intents and purposes, and hot or cold it will flow 300 all day long. Warm air will be less dense than cool air so when the warm air is compressed the resultant pressure in the cylinder will be lower as there is more void around the air molecules for them to compress into before the pressure can rise, but this all happens in the blink of an eye, all you noice is a resultant loss of power. Do you ever notice how good the car feels on a crisp winter morning. That is not a placebo effect that is real and it is all because of the lower temperature of the outside air. Incidentally if the temperature drop across the intercooler is 50 deg C, the inlet air will be bonnet ambient minus 50, so higher in equals higher out.