ok buddy of mine comes over telling me about how hes going to recuce turbo lag on his T88 turboed rx7. compressed air tank (lil 10 gal one or whatever) sprays air into manifold to spool turbo a bit before launches. great idea. and very possible to do.

so my question is. say i have a compressed air tank chillin in the hatch. instead of being connected to the turbo manifold its connected to my air intake, post filter. how would my motor react to a nice blast of compressed air? **** ton cheaper than n2o. refillable at gass stations and at home. i understand that if its a great enough pressure to actually do anything id have to adjust fuel curves possible timing for it. just wondering if anything cool would happen as a result.

you runing nitrous? nope compressed air.

opinions welcome and needed


[Modified by TorteX, 1:08 AM 5/3/2002]

 

I think your friend needs to realize exactly how much air flows through a motor ...

 

My guess would be that if it did work then you also need to raise the fuel pressure to match the added air. But I'm just guessing and trying to use common sense.

 

hmmmm Good luck man anything can happen :go to sleep dustin: j/k

 

right. well i can see this set up working more efficiantly thu and air intake than a turbo definatly. however aparently it has been done before to spool turbos. aparently some peeps have a air compressor running off the pullys to compress air. also its a rotary engine and he knows em a **** ton better than me.

but im thinking blast of air into intake could possible create a boost like effect

 

if you attach the air nozzle deal (blows air to blow **** off etc) to a air compresser as like 40 psi is blows quite hard. very good for cleaning off things. have the same set up but chillling in the cabin.

air tank at 160psi -> line -> lil sprayer deal -> vacume line running into intake.
youd have to keep the final vacume line relitavely small in diameter to keep up pressure from the sprayer. i'll post pics tomorrow air tank would have to be modded but i think its quite possible.

 

But understand that if you have tons of flow (i.e in a motor) it is almost impossible to sustain pressure. That's why turbos flow SO MUCH air to create positive pressure.

Pressure from an air compressor (even 160psi) is at zero flow. Your average air compressor can flow under 10cfm@160psi. Now imagine a motor, say 1.6 liters. It is going to flow 1.6 liters of air every 2 rotations of the crank, so if you are at idle (say 750rpm) in a minute you will flow 600 liters of air. Now rough estimate 4 liters / cubic foot of air you have 125cubic feet per minute.

125 > 10.

I think you fundamentally misunderstand the relationship between pressure and flow.

Dustin

 

I've heard of getto superchargers at sears too, But I just call them leaf blowers.. Most turbos or superchargers flow a least 1000cfm. It's funny you bring this up though b/c when my zex bottle is out of nos, it still sparys cold air in the motor... 17.6 on the motor, 16.4 sparying regular air, and 15.1 with a full bottle... Kinda weird... Even though I think the idea of compressed air sounds kinda silly, why wouldn't it do the same thing as my nos system ?

APEXI

 

Horribly enough, I've been over this before, either here or super honda, but anyways, here we go again. To sustain enough air to flow into your engine at an increased pressure, you would need to run at least a 2 inch pipe from the tank to your engine and have enough reserve in the tank to supply a pressure increase. It's the same theory as a turbo, if you didn't need all that flow, then you could just run a vaccum line from the turbo into your manifold, but it doesn't work that way! I won't go on endlessly about why it doesn't work, if you want more then just do a search and find some of the old info. Perhaps your freind with the RX-7 was talking about running an air line ontop of the turbine in the turbo, in which case it could be slightly effective to reduce turbo lag in between shifts, but really only practical for 1/4 mile use.

 

yeah he was going to run it to the turbine. well i figured it was worth a shot

guy running cold air w/ zex kit, you notice any diference over stock?

 

I felt a little more powerful, but I knew it wasn't NOS !!! I can't believe it made such a difference, but the next run with a full bottle I knew I was FLYING !!! 75hp on a 92 hp motor, Sweet !! 116 oct of course..

 

The same Idea was brought up at Camaro Tech about a year ago. To make a long story short. There will be NO noticable gain.

 

Actually, whatever these people say, I think it would be a good idea.

Not that it will give you a ton of power like Nitrous, but the actual cooling effect that the air would give coming out of a small nozzel, would definetly be benificial.

I might look into that

 

I think only people with no engineering background are fooled into thinking this is a good idea.

 

Using compressed air in the exhaust manifold to spool up a turbo faster is an entirely different concept from spraying compressed air into your intake tract.

Using compressed air to spool up a turbo makes sense. If a nozzle blows directly on your turbine blades it'll have a noticeable effect on how quickly the turbo spools up.

Trying to make a supercharger out of compressed air just plain out won't work. Any nozzle you use won't flow enough cfm to make positive manifold pressure. As soon as the air leaves the nozzle and enters the manifold it expands. Bye bye "pressure."

Also, to create a supercharging effect you would need to have the compressed air flowing for an extended period of time as opposed to just a short burst to get a turbo spooled up.

 

thanks for the info. just was wondering if his turbo lag solution could apply some where else

 

This could potentially reduce turbo lag if he were to pipe it into the exhaust manifold ahead of the turbo. I seem to remember some Mitsubishi rally cars having something similar, where the blowoff valve was plumbed to the turbo somehow, feeding the turbo air under closed-throttle conditions. Can't remember what used it or what it was called, though...

 

Is compressed air Co2??? hehe that otta be good for your engine. So is it Co2???

This wont work at all tho but the spooling up the turbo soundsa sweet. I can put the nozzel in th hole in the HF manifold where the o2 sensor goes and put the o2 sensor in the downpipe......... wait no i still think its a waste of time.

But would be cool if it worked

 

It's called "anti-lag."

An explanation of how the system works from http://www.rallycars.com/Cars/bangbang.html:

When the driver lifts his foot from the gas pedal the ignition timing is altered with sometimes 40° or more of retard and the intake air and fuel supply mixture is made richer . This results in air/fuel mixture that keeps getting in the combustion chambers, through an additional bypass valve, when the driver no longer accelerates. The ignition being retarded, the air/fuel mixture reaches the exhaust tubes mostly unburned. When the spark plug fires, the exhaust valve is starting to open due to the ignition retard. Additionally, the exhaust temperature being extremely high, the unburned fuel explodes at the contact of the exhaust tubes. Luckily the turbo sits right there and the explosion keeps it turning (otherwise it would slow down since its intake, the exhaust gases, is cut-off). The effect is a vastly lower response times with some downsides:

-A quick rise of the turbocharger's temperature (which jumps from ~800°C to the 1100°C+ region) whenever the system is activated

-A huge stress on the exhaust manifold and pipes (mounted on a street car a bang-bang system would destroy the exhaust system within 50-100 km)

-The explosions which occur in the exhaust tubes generate important flames which can, sometimes, be seen at the end of the exhaust tube

-Reduced engine brake

The bang-bang system owes its name to the loud explosion noises one hears whenever the driver lifts his right off. Depending on the implementation, ALS systems can be more or less aggressive. While the systems mounted in Toyota and Mitsubishi racing cars are relatively smooth and noiseless those fitted in Ford and Subaru cars are much more noisy and aggressive. Most racing implementations have user selectable anti-lag settings depending on the terrain, usually three settings can be selected by the driver going from moderate to very aggressive.

Note that some regional or national European events prohibit the use of ALS systems while more and more WRC events regulate the noise levels allowed by competition cars effectively disabling ALS.

The reason the Toyota and Mitsu implementations are smoother is because they use a manifold like you described with the BOV venting into each runner. This is the Toyota manifold:

 

Compressed air wouldn't do anything....... now compressed OXYGEN..... then you've got something...... until it goes BOOM!!!

 

It is N2O. THERE IS NO AIR IN THE TANK DUMBASS!!!

Compressed air is COMPRESSED AIR 78% N2, 21% O2, 1% Corn sweetener, I think. percentages may be off.

-Dustin

 

Gee, don't I fell DUMBASS, mi 1.300 litr motr wuns 15.1 butt im a dumass... Wow, someone needs either zanex or less anarol ( steroid )...

 

See nitrious does NOT burn. It is a super hydrooxygenated mixture witch breaks down into nitrogen and oxygen at about 550* Ferenhgeit. Thus providing more air into your engine .

 

right nitro simple supplies more pure oxygen during combustion. pure oxygen is basicly flammable (kinda, big time catalyst). increases explosions by a **** ton. get a test tube upside down, pump pure oxygen into it. hold a match under neathe test tube and it'll POP. like a small firecracker. my idea wouldnt use nitro. regular air. so obviously there wouldnt be nearly as much oxygen for combustion as w/ nitro. however if it could be used as like FI at the flip of a switch it would be cool. but i guess you cant pump enough air for it to actually work

mrfatbooty, w/ the text. this set up will provide boost even at idle then? or only inbetween shifts when bov releases pressure back to turbine. i guess hes just trying to build up some kind of boost for launch. he could rev higher but i garentee tires would never hook up. i dunno


[Modified by TorteX, 1:40 AM 5/4/2002]

 

It's to keep the turbo spooled when the throttle closes. In practice what happens is you let off the throttle (to decelerate or to shift) and there's a big explosion in your exhaust manifold to keep the turbo spooled up. Get back on the gas and the turbo's still spooled. Now that the WRC cars run sequential gearboxes (i.e. F1 style) the throttle stays open on shifts and the anti-lag is only used on deceleration. If you ever watch a WRC race and hear the cars pop/sputter/shoot flames out the exhaust while they're slowing down that's the anti-lag. As far as I know Mitsubishi and Toyota were the only manufacturers to plumb the BOV into the exhaust manifold and Toyota doesn't compete in the series any more. Compare say an EVO decelerating to a 206 and the difference is quite clear.

If you want to reduce lag at launch get a 2-step rev limiter. Also referred to as "launch control" by Hondata et al. Basically the ECU (or ignition box like an MSD Digi-6) has a rev limit set at your optimum launch RPM. It's only active while the car's not moving and your foot's on the clutch. Floor the gas, motor bounces off the limiter. This keeps the throttle open and your turbo spooled up.