V2Rocket

FIFY

luftpirate

I bet you a pack of Marllberoze it works on my Camaro.

V2Rocket

as i said before, the concept of ram-air is that you are going fast enough that incoming air backs up on and compresses itself so that you get a sort of supercharging effect. this is the principle that ramjets/scramjets rely on. the air when compressed resonates at the speed of sound but you are going faster than that so it can't bounce out of the intake.

automotive 'ram air' setups put a scoop or intake of some type in a place that will be in a high pressure area so that it is best for drawing intake from. cowl induction works the same way. cutting a hole in your hood to feed your air filter won't do you any good. it would probably run ok but you wouldn't get quite as much potential as if the intake were in a high-pressure area. at subsonic speed the 'ram' is so minimal it might be a few percent at best.

ritzblitz

Way less. Highly engineered cars such as Ferrari 458 see about 1% IIRC at ~180mph. And they designed it to have a "ram air" effect.

Unless you design the car around the concept of ram air, you might as well forget about trying to increase power output through a ram air effect. But anyone who tries to do this will most likely see gains, probably because they modified the intake in a positive way, i.e. elimintating the j boot bend, provided ducted cold air to the engine, etc.

FRporscheman

I was just about to say, it looks like the biggest benefit of that setup is the elimination of the j-boot.

MAGK944

I think the j-boot was put there for a reason, to isolate engine vibration from the body mounted AFM. I now see the AFM in a more vulnerable position, more firmly attached to the engine not the body and more susceptible to failure. If that was a MAF it wouldn't matter as much but these AFM are a lot more sensitive to vibrations.

ZR8ED

[QUOTE=Dimi 944;8955835]Done testing the new intake set up!
Overall, there is no change in the average horsepower. However, between 5000 and 6400 rpm the car made 136 HP - gain of 4 HP. Between 2000 and 5000 rpm the car made 128-129 HP - loss of 4 HP.
Having in mind, I predominantly track the car the gain does help me. Also, my friend and I are working on an air scoop/collector to generate/simulate ram intake. This should lead to some power increase at speed. However, more than likely the mapping has to be changed because the ECM wouldn't know of the increased air flow/pressure at WOT at speed.

Btw, the car has stock exhaust and MaxHP chip.QUOTE]

Thanks for the testing! Interesting results. So far it appears that for a street car that is driven under 5k rpm most of the time, the sacrifice may not be worth the gains. BUT! Could you describe that intake infront of the afm? Is there an air horn inside there to channel air into the square port similar to the one inside the stock airbox? if not, I could see how hp would be lost in the low end.

SpeedBump

Thanks, may have to run a couple of cars over there to get some numbers. 6 miles from my office not too bad

M758

Interesting. More peak power at the expense of some mid range. Wonder what the A/F ratios are doing. As for losing mid range.... it realy depends. The meat of the RPM band on track is 4000 to 6000 rpm. That is where you spend 95% of the time when on track. There maybe a few places you run under 4000 on track, but down at this speed you probably are better off in lower gear. So really you what max avergae power over that 4000-6000 rpm range. I once compared ym 131 peak hp dyno to a 138 hp peak dyno. I was happy with my 131 peak because I made more power right to about 5700 rpm. My power dropped off and the other motor peaked.. that last 300-500 rpm is ok to have, but I would rather have more from 4000-5700 rpm. For track car what goes on at 2000 rpm is irrelvant. Heck what happens below 3000 rpm is pointless. 3000 rpm = low point on the warm up.

As for ram air.. Well despite my surprise... it works. We have data on 944 spec cars that show that ram air will increase top speed on long straights. I think you start to see gains at about 80 mph and up and mostly in 5th gear which when using 225/50 R15 tires you hit around 100 mph. Not worth it for road speeds, but on the track it does appear to help Vmax. This based on data from couple cars. Apparently no need to adjust tune on the car either, but I am not sure if mixture goes lean at high speed. I suspect it will, but not sure if its still in the safe range.

Now how to do it. 944 spec rules require stock from AFM back to the intake so we run stock NA j-boot. The best way seems to be to direct the stock snorkle from the fender to the fog light opening. This are already is natural high pressure. Next time on track I will try this by redirecting my brake duct to the intake. Not sure what I will do about the brake duct, but I figure it is with a shot. Only problem is my next race will be on track that does not use 5th gear so the effect may be limited.

Now one thought on metering is that if AFM has not been pegged out under normal conditions it can still meter some positive pressure. The AFM is simple potentiometer off a calibrated flapper door. The more air that goes in the more the door is open. Then more fuel is metered. If WOT does not for the door to limit of the travel it may be able to meter a slight positive pressure and ensure proper fuel flow. The real way to check is to record the AFM voltage with and with out ram air to see if the flapper door is "more open" than without ram air.

V2Rocket

ditching the AFM will help more...

944CS

ram air absolutely works at "automotive" speeds. There is plenty of data to show it. Hell even Porsche themselves claim 10-15hp gain at speed (I forget exaclty what they quote but like 100 or 115mph)
on 996GT3 & 997 GT3 with their rear deck inlet scoops - this is about 3-4% depending on which model you are talking about

ZR8ED

A well designed system of "ram air" has an effect of approx 1psi of boost at 100mph. Some people seem to mix up the terms "ram air and "cold air" both of which are benificial, but are executed differently.

Going MAF will help yes, but at a cost of $1k to buy and install properly, and will net you 5-8hp?? So far this experiment netted 4hp at a cost of a used manifold/tb, and some time and creativity that would cost less than a $100.00. (25$/hp or $125.00/hp)

86 951 Driver

You may get more since you are porting the Turbo manifold and going to run a bored TB. I would still go through with your project. Also There is a Miller MAF system I believe that is available now for the N/A that isn't $1000.

Dimi 944

Dyno sheet has been added to the first post as well as the corrected power and torque numbers. It appears that I did not read the results correctly. The car made 3 HP more with both set ups that what I thought it did.

luftpirate

Even with RAM air you aren't going to see over 1 BAR.