McLaren F1 - ask a question........

[LuckyP]

Thought this was interesting....

How many of us know for sure we are getting positive induction pressures at speed?

"THE MCLAREN F1 HELD THE PRODUCTION ROAD CAR WORLD SPEED RECORD AT 240.1MPH/386.7KPH FOR 7 YEARS, AT THE TIME THE RECORD WAS SET I UNDERSTAND FROM WATCHING FOOTAGE THAT THIS MAXIMUM WAS LIMITED BY GEARING AND NOT POWER, HOW FAST COULD THE CAR HAVE GONE WITH DIFFERENT GEARING?" (from Guy Turner)
The short answer to this question is probably not any faster.

A vehicle's maximum speed is governed by its engine power, air resistance (drag), rolling resistance as well as overall gearing. Ideally, maximum speed should occur at maximum power in top gear for a correctly geared peformance car. In the case of the McLaren F1 there is an additional factor - the induction inlet was designed to ensure positive pressure in the air box. That is, it's forward facing position above the cabin ensures air is forced in to the air box resulting in the internal air pressure increasing with speed - similar to a modern Formula 1 layout. The higher the induction air pressure, the more power can be generated - something that has never been quantified on the F1. The ram effect therefore pretty much equated maximum power to the speed that was achieved, and it is unlikely that a change of gearing would have affected this.

Maximum speed however was never one of the guiding design principles behind the F1. The F1 will clearly be remembered for more than just that one world record speed run.

[Steve_D]

A Megasquirt EFI ecu uses a MAP (Manifold Air Pressure) sensor to determine what load the engine is under and from that gauge how much fuel to add.
Should be possible to fit a similar sensor inside the inlet or top of the clip to see if a pressure exists.

Further thoughts. A manometer (simple water filled U tube) could be used.
In order for this to be valid, if reading from inside the cockpit, you would have to assume or try and arrange for the cockpit to be neutral pressure.

Could be an interesting hour spent with plastic tubing.

Steve

[LuckyP]

Steve_D said:

A Megasquirt EFI ecu uses a MAP (Manifold Air Pressure) sensor to determine what load the engine is under and from that gauge how much fuel to add.
Should be possible to fit a similar sensor inside the inlet or top of the clip to see if a pressure exists.

Further thoughts. A manometer (simple water filled U tube) could be used.
In order for this to be valid, if reading from inside the cockpit, you would have to assume or try and arrange for the cockpit to be neutral pressure.

Could be an interesting hour spent with plastic tubing.

Steve

Plastic tubing is our plan. But yes good thought - the cabin pressurises at speed!! - I'll try to catch vid of it!!

[Pb3]

Okay, I will do a test on Sunday. I am at RAF Marham for a trackday, I run Megasquirt and will be topping out at 172 to 176 mph (depending on my chosen rev limit). I originally set my maps up to a maximum of 105KPa (around a 100KPa is normal atmospheric sealevel pressure), why 105, well to allow for any slight ram air affect, but to date I have not really proven anything. All my engine intake air comes from the top air scoop and is completely sealed around the filter, the MAP sensor should hopefully read more than atmospheric at WOT (wide open throttle), we will see.

Later...

[LuckyP]

Pb3 said:

.....All my engine intake air comes from the top air scoop and is completely sealed around the filter..

How have you done this? Are you saying that all air for your engine can only come from the top air scoop?

[TuxMan]

i,ve been looking at the carbon reveri side pods should be able to connect straight onto my cold air pickup with a inline air filter should give me a shed load of positive pressure ....maybe !!

[eliot]

Pb3 said:

Okay, I will do a test on Sunday. I am at RAF Marham for a trackday, I run Megasquirt and will be topping out at 172 to 176 mph (depending on my chosen rev limit). I originally set my maps up to a maximum of 105KPa (around a 100KPa is normal atmospheric sealevel pressure), why 105, well to allow for any slight ram air affect, but to date I have not really proven anything. All my engine intake air comes from the top air scoop and is completely sealed around the filter, the MAP sensor should hopefully read more than atmospheric at WOT (wide open throttle), we will see.

Later...

Yes this is an easy thing to see with the MS, remember to start your datalog before starting the engine so you record the air pressure for the day.

[Pb3]

LuckyP said:

Pb3 said:

.....All my engine intake air comes from the top air scoop and is completely sealed around the filter..

How have you done this? Are you saying that all air for your engine can only come from the top air scoop?

Yes all air is from the top scoop.

Here are a couple of pictures (in the early days):




Both the filter tray and the air box have now been covered in heat matting and an inner lip added to the air box with 1 inch foam to allow it to seal against the outer edge of the filter/tray when closed.

I have the temperature senders (one for my dash, one for MegaSquirt) in this air box (not as shown in the above pic, just above the filter and only ever see intake temperatures 2DegC above ambient, even when engine bay temps hit 50+

[LuckyP]

I vote you the man for weekend - very interested in the results

[k wright]

Very nice, assume that the airbox is the one sold for "dragsters". Any details on it and the filter you have? The glass box that you've attached to the engine cover should be an option from the factory as is the Stack panel pod.

Thanks for the photos.

[Pb3]

k wright said:

assume that the airbox is the one sold for "dragsters"

No, although I did sort of copy the idea after seeing one in the Summit Racing catalogue. I was never sure how well a bought one would fit to my throttle body (as it has a slightly non-standard filter seat).

As for the filter, I spoke to a K&N guy at the Autosport show and he did the calcs and suggested an off the shelve part, which is a CORVETTE 5.7L F/I 1990-96 filter (pn: 33-2035) which is good for something nearing 600hp I seem to remember.

The only prob with an ally filter tray is with heat, that is why I have now insulated in heat mat, and use a 1" poly carb spacer between the intake manifold and the throttle body.

[USAGTRMAN]

My Reverie intake took a little modification but ended up fitting quite well.



Brad Z

[Pb3]

I have take a few more pictures, as it is today:

Cut down and insulated filter tray, with sensors mounted above:


Here is the air box, now with the inner lip and 1" foam to provide the seal, it also holds the filter down in the tray:


Closing the rear clip:


I have taken some logs from my trackday and will post the pressure results very soon.

[LuckyP]

PB -any joy with those figures?

I'm having a development day at Dunsfold on Friday.

Trying a few things:

1) Vmax with air filter on
2) Vmax with air filter off - gauze on
3) Vmax with air filter off - gauze on - LuckyP 'air ram special' in place.

No other variables

[GTWayne]

I am all for R & D ( if nothing else it is just a real good excuse ), but I think that you would be able to detect more of a performance variable with an ambient temperature change than the filter on\of type testing that you have planned P. If it is possible to measure any type of improvement it will only make a difference in real world terms if instigated along with a few other like minded mods. Alternatively, bite the bullet and fit LS7. you know you want to

[Pb3]

Well, having a look at my logged data does not suggest any real ram air affect at all. One log showed an atmospheric pressure of 100.9KPa (at 0rpm) and at WOT I got around 99.8 to 100.5KPa. I could always have a restrictive throttle body, but I did have it bored out to 4 x 38mm so should be more than enough for my power. I suppose looking at the data you could say that I have the inverse of a ram affect and suggesting negative pressure at the scoop openning, but I don't want to admit to that The main thing for me is still getting cool air into the engine for which the top scoop if definitely good for.

[LuckyP]

GTWayne said:

I am all for R & D ( if nothing else it is just a real good excuse ), but I think that you would be able to detect more of a performance variable with an ambient temperature change than the filter on\of type testing that you have planned P. If it is possible to measure any type of improvement it will only make a difference in real world terms if instigated along with a few other like minded mods. Alternatively, bite the bullet and fit LS7. you know you want to

My good man,

After last the last Vmax event where speeds varied from 171 to 188, I would agree that variable do effect the only measurable I have on offer - the speed. Trouble with Brunters was that the variable included:

1) Filter on/off
2) length of track
3) Temperature (got sunny towards the end of the session)
4) Track condition (dried out towards the end)
5) Gear change RPM
6) Corner exit speed
7) technique

So - coz I have a bee in my bonnet about the amount of air (cool or otherwise) that is getting into the engine - I want to try and change only one thing at a time by keeping all other things as constant as possible.........

.......bare with me on this one!!

[andygtt]

That was what I was afraid of, negative pressure at the scoop...... we already knew that the negative pressure tried to open the tops of the doors at speed.

I still think boxing out the air filter is a good idea just to get cool air.

[LuckyP]

Pb3 said:

Well, having a look at my logged data does not suggest any real ram air affect at all. One log showed an atmospheric pressure of 100.9KPa (at 0rpm) and at WOT I got around 99.8 to 100.5KPa. I could always have a restrictive throttle body, but I did have it bored out to 4 x 38mm so should be more than enough for my power. I suppose looking at the data you could say that I have the inverse of a ram affect and suggesting negative pressure at the scoop openning, but I don't want to admit to that The main thing for me is still getting cool air into the engine for which the top scoop if definitely good for.

1) where is your pressure sensor?
2) What speed did you get to?
3) what temp was your air temp sensor reading?

[GTWayne]

andygtt said:

That was what I was afraid of, negative pressure at the scoop...... we already knew that the negative pressure tried to open the tops of the doors at speed.

I still think boxing out the air filter is a good idea just to get cool air.

As you know, I have dealt with the negative pressure at the scoop problem by replacing the scoop with an enlarged and raised item but the main reason that I favoured boxing the filter and ram pipes in was as Pb3 has said, to at least try and keep the heat from the engine bay from being inducted into the inlet. I don't have any hard evidence to back up these theories on the GTW ( although most modifications that have been carried out have already been tried and tested elsewhere first ) but suffice to say that anything that is done like this will at worst not hinder performance, even if it should fail to enhance.