25 replies to this topic

[D 'n A]

Its basically a thermostat. When the engine and weather is cold hot air from the exhaust is fed into the airbox.

This helps warming the engine up quicker and saves some fuel in the process.

[OJDee]

Its basically a thermostat. When the engine and weather is cold hot air from the exhaust is fed into the airbox.

This helps warming the engine up quicker and saves some fuel in the process.

Good to know - thanks

[rock1day]

I have the typical cone filter since had my 998 rebuilt and want to try Keith Calver's idea drilling holes in an original filter case. The engine runs lovely but it is too loud for me after 20 minutes of fast driving.

 

Calver's idea allegedly gives even better performance than the cone filter.

What about trying a Metro airbox?

 

There cheap and seem to have a larger air inlet to the filter element.

[Compdoc]

I think the Metro airbox is pretty efficient, but the routing of the air as it enters the airbox seems restrictive. You can see there is a 90 degree curve downwards into the airbox, then another 90 degree curve to get to the filter.

I blanked off the hot air intake and completely cut out the two 90 degree curves and repaired with bumper repair. I have an old vacuum cleaner with an indicator that shows the amount of restriction in its flow, (to tell you when the bag is getting full), and I used this to measure the flow, (a bit crude, I know), but it definitely improved the flow overall.

 

 

[sonscar]

whilst servicing my Rover V8 3.5l I measured the intake to the air filter after reading this thread to be approx45 mm.By comparison the intake on my 998 Mini is 40mm or so.In terms of area this represents some increase but not massively(200 bhp 190ft lb torque when new)In terms of road performance we may be chasing imaginary gains.

My RV8 engined MGB had a cone filter as it seemed that it was THE ONE to fit.In traffic the intake temp rose so much the motor performed very badly with pinking aplenty when you first opened the throttle.The filter was over the exhaust pretty much like a Mini.Fitting the standard airbox poking into the grille reaped benefits.Just my old man experiences,Steve..

[rock1day]

I think the Metro airbox is pretty efficient, but the routing of the air as it enters the airbox seems restrictive. You can see there is a 90 degree curve downwards into the airbox, then another 90 degree curve to get to the filter.

I blanked off the hot air intake and completely cut out the two 90 degree curves and repaired with bumper repair. I have an old vacuum cleaner with an indicator that shows the amount of restriction in its flow, (to tell you when the bag is getting full), and I used this to measure the flow, (a bit crude, I know), but it definitely improved the flow overall.

 

I believe it`s less about the size of the entry pipe and more about how much of the filter is exposed inside the box?

 

I like the sound of the internal modifications (completely cut out the two 90 degree curves and repaired with bumper repair) you've made, but I can`t picture them? 

 

Could you add pictures if possible?

[Compdoc]

You can see from the original picture that the inlet swoops downwards.

 

So this portion of the curve needs to be removed as well as the flat piece in front of the curve to allow a straight pipe to be inserted.

It creates rather a large hole which looks a bit daunting and feels very flimsy before you get and bumper repair on it.

I used an off-cut of the carbon fibre inlet pipe, which was 50mm, obviously the same diameter as the airbox inlet, and cut away the plastic until I could slide the pipe in from the inside of the airbox. This ensures that the size of the air inlet will be 50mm all the way to the air filter.

I covered the tube with some Teflon oven liner and sloshed on the bumper repair paste.

I used the same repair paste to ensure a smooth flow once in the airbox.

Once set, I slid out the tube and peeled the Teflon liner from the inside of the opening. Its pretty solid, but you can apply more paste if you want.

I finished it off with some black bumper paint.

I hope this is some help.

 

[humph]

Before spending time modding a metro air box for your HIF38 check it will fit. There are numerous posts on here saying the posters can’t get this airbox to fit a HIF on a Mini, it catches on the bulkhead or scuttle.  Most advise the use of the old round Mini airbox, modded as suggested by Vizard.  This is the route I had to go to get a box that fitted. 
 

Edited by humph, 20 April 2022 - 10:17 PM.

[rock1day]

You can see from the original picture that the inlet swoops downwards.

 

So this portion of the curve needs to be removed as well as the flat piece in front of the curve to allow a straight pipe to be inserted.

It creates rather a large hole which looks a bit daunting and feels very flimsy before you get and bumper repair on it.

I used an off-cut of the carbon fibre inlet pipe, which was 50mm, obviously the same diameter as the airbox inlet, and cut away the plastic until I could slide the pipe in from the inside of the airbox. This ensures that the size of the air inlet will be 50mm all the way to the air filter.

I covered the tube with some Teflon oven liner and sloshed on the bumper repair paste.

I used the same repair paste to ensure a smooth flow once in the airbox.

Once set, I slid out the tube and peeled the Teflon liner from the inside of the opening. Its pretty solid, but you can apply more paste if you want.

I finished it off with some black bumper paint.

I hope this is some help.

 

Very helpful, thank you. 

Edited by rock1day, 23 April 2022 - 10:10 AM.

[rock1day]

Before spending time modding a metro air box for your HIF38 check it will fit. There are numerous posts on here saying the posters can’t get this airbox to fit a HIF on a Mini, it catches on the bulkhead or scuttle.  Most advise the use of the old round Mini airbox, modded as suggested by Vizard.  This is the route I had to go to get a box that fitted. 
 

Very smart, is it a grey sign written Mini van by any chance?

[humph]

Very smart, is it a grey sign written Mini van by any chance?

 

 

 

 

 That would be nice! It's my Mk3 Riley Elf that I'm just putting the finishing touches too.