Forced induction cars?!!??

[All Wheel Drive]

It seems to me that there are some people (people with knowledge in this car business, seriously speaking) on this forum who don't like cars that have forced induction... Could this people explain their choice so that I understand a bit more about cars...? :roll:

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Hallo All Wheel Drive,

 

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[djfux69]

i think the people that dont like FI (not me!!!!) dont like it because they feel it is cheating. they feel that there is nothing like a fully tuned NA engine. i agree that NA engine are great when you can get serious power... but even a fully tuned NA motor isnt really " fully" tuned until it has FI. Forced induction is the final frontier so to speak. i love it.

[All Wheel Drive]

The idea of FI is that high amounts of power and torque are delivered from low rpm through high rpm. The problems with turbos is that they take some time until they fully supply the engine with the desired amount of air (turbo lag, I think)... With a compressor the lag is not so obvious and there are ways of diminuishing it on turbos, too, right? So, beyond the turbo lag, I don't see where the problem is.

Maybe some believe that the good tuning is without any FI, but I don't share that opinion either. An FI engine has the elements of the NA tuning but also the FI systems... so it's more complex, I'd say.

[djfux69]

true. turbos have turbo lag. but give you serious power. superchargers ( compressors) dont have lag but they cause parasitic drag because they are run off of the belts. in most cases it is around a 10-20% loss in power through the belt. granted it will still give you more power than stock but not as much as a turbo. antoher thing is turbos can run a lot higher boost(psi) and give more power, while having no power loss like a charger. also turbos to me are more efficient because they only run ful boost when you give it full throttle. superchargers are full boost all the time, with exception to the superchargers on MB, which i heard has a clutch which disengages power when not under full throttle.... i like this idea and i dont, to me its just another thing that can break on a car,.

[All Wheel Drive]

Agree, turbos can deliver more power and torque than the superchargers. But good turbos like those u say are realy expensive. For high psi u need ball bearing turbos and that does not usually come on stock... A good compressor it's simpler and not so expensive... maybe that's why amg used to use compressor not until a few months ago (S65 and Cl65, speaking).

Anyway, I didn't want to start a turbo vs compressor discussion: just wanted to know why not FI?

For example: the new m5 should have like 500hp; the new e55 has 463hp. Let's assume the amg engine slims up and it weighs as much as the v10 on the m5...(it's cast iron + compressor vs aluminiun and magnesium alloy) and we put the 5.4l V8 compressor amg it the m5 body. Who would take the lead in acceleration: the classic m5 or the "amg m5"? (surely a difference of at least 150Nm of torque means something...)

I have a lot of respect for both brands, but I can't stop myself in asking what if...

[djfux69]

im not sure if i understand your question.... you are asking if a turbo motor in the M5 would be good? i say yes! bmw isnt known for using FI... except on tdi?? im not sure. anyway if you took the e65 motor and put it into the m5 it would be phenominal... the new MBs have serious power.

[All Wheel Drive]

I say: take the amg engine that's on the e55 and put it in the new m5 (the one with the v10 NA).

Who would win in a straight line: the m5 with e55 engine in it or the m5 with it's stock v10 (NA)?

I say: why not FI?

[thepolarfoxqx]

Easy answer to your question, the M5 with the M5 engine. It has a very long flat torque spread (just like the AMG motor), but the BMW 5.5L V10 is close to 200lbs (supposedly) lighter than the AMG motor, which would make a nice difference in acceleration, plus the 5.5L V10 has tons more top-end power because it isn't supercharged.

My beef with forced aspiration goes like this. I don't think it is awful, i've had turbocharged cars before (a '92 Saab 900 Turbo and an Audi A4 1.8T), they are not balanced enignes, power delivery is not linear, the turbo lag is frusterating, as you have to plan power transitions ahead to take into account the turbo speeding up and slowing down. It also raises the temperature of the engine signigantly. Also, above -oh, say 6,500 rpms, turbos also make a lot of drag, just like superchargers. That is why if you strapped a turbo or a supercharger on to, say an M3, which peaks at 8,000 rpms, you would definately gain bottem end, but you'd loose top end, and in fact, your horsepower would not likely increase much, it would just be shifted from top-end to bottem-end. That isn't a good thing - here's why. When you race, or do any sort of straight line hard acceleration, you want to stay in lower gears as long as you can, so say in a race, you will stay in the top half of your rev-range the entire time, to take advantage of extra torque off gearing. If all of your power is concentrated down low, it doesn't help you much, but if your power is up high, it works perfectly.

Also, turbos increase oil temperatures signifigantly, which can adversely effect long term durability.

Superchargers, while not very laggy, start to become parasitic even lower than turbos, and per how much drag they produce, they make less boost than a turbo.

In terms of handling, you can't have abrupt changes in torque, like the sudden boost of a turbo spooling up. Some turbo cars make very little lag, and work very well, like the A4 1.8T, but it's 1.8L engine with a turbo made 150hp, and right now my naturally aspirated 318i's 1.8L makes more than that, what good did the turbo do?

The saab 900 i had a 2.0L making something like 185hp, but it had turbo lag in the days.

Forced aspiration is a cheap, easy way to get more power. You could get the same power naturally aspirated by tuning, refining, and enhancing breathing, but that is more effort, and often more money to develop than forced aspiration. Forced aspiration however does give a nice hard kick down low, which has it's usefulnesses.

[reggid]

AWD: You can't simply swap engines from e55 to M5 without mating it to a matched gearbox!

M5 engine will rev to 8000+rpm ( Vs 6100rpm) allowimg the use of bigger reduction ratios (to give the same max speed at end of each gear).

Its not so important to have big engine torque since you can gear the car down to give alot of torque at the wheels and hence give good acceleration, BUT you also need an engine that can rev otherwise you'll need to shift every 30kph.The M5 engine will be better because it will be able to rev.

There is a limit to how much useful torque you can put to the ground in a road car. Most people don't realise that the e39 M5 and e55 put about the same peak torque to the road sice the M5 is geared differently, the e55 wins by virtue of a flatter torque curve more that anything else. Power is not as directly important as most people think.

Torque = Power/angular velocity

If you have both cars delivering their peak power at the same wheel speed the car with the most power will have more torque.

[djfux69]

AWD: You can't simply swap engines from e55 to M5 without mating it to a matched gearbox!

i think he was speaking hypothetically. power figure wise. not actually swapping the engine.

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Hallo All Wheel Drive,

 

schau doch mal hier zum Thema Verschiedenes über Autos (Anzeige)? Eventuell gibt es dort etwas Passendes.

 

Der V16 Motor zum Selberbauen (Anzeige) ist auch genial.

[bleh]

Also, above -oh, say 6,500 rpms, turbos also make a lot of drag, just like superchargers.

that depends solely on the turbo(s) used.

Also, turbos increase oil temperatures signifigantly, which can adversely effect long term durability.

common you know theres a way around it...oil coolers? heat sheilds?

right now my naturally aspirated 318i's 1.8L makes more than that, what good did the turbo do?

sorry to doubt you but im going to have to see a dyno plot to believe that your 318 makes that with only i/e and no a/c.

Forced aspiration is a cheap, easy way to get more power. You could get the same power naturally aspirated by tuning, refining, and enhancing breathing, but that is more effort, and often more money to develop than forced aspiration. Forced aspiration however does give a nice hard kick down low, which has it's usefulnesses.

you really cant get the same power from na tuning. theres a reason the amount of psi in kart racing is limited, its just an unfair advantage.

i thought that the most efficient superchargers took 20% off the crank. i thought most were worse.

[SERGIOE34]

I agree with everything fox said.Who wants to wait for power to kick in at a certain rpm anyway?It should all be right there once u hit the gas.I also dont like the sound of forced induction engines.Nothing beats a highly tuned and refined natruly asperated engine.There just the best.

[All Wheel Drive]

So, if I understood well... : the advantage of well tuned NA engines is that when they hit peak revs they are in full power and also have a good amount of torque. As for the forced induction engines a big amount of torque is given down in the rpm range, but not in the upper half of the rev range, where the engine should be geared as it exploits the torque better.

Could someone find some diagrams(torque/power) of an FI engine and a NA engine having nearly the same displacement so than I can understand better the distribution of power and torque along the rev range?... With some comments I think it will be ideal... :roll:

[djfux69]

I agree with everything fox said.Who wants to wait for power to kick in at a certain rpm anyway?

im sorry to inform you that NA cars need to wait for their peak HP just like FI cars do...

It should all be right there once u hit the gas.

should be... but its not. with an NA engine you need to wait for the power band to get power, whereas with turbo cars (depending on the gear you are in) power is a few rpm away. especially in upper rpms. granted a larger turbo will have more lag, but on engines that are tuned for the turbo they will spool much much faster.

I also dont like the sound of forced induction engines.

wow... i think thats the first time i have heard anyone say that...

Nothing beats a highly tuned and refined natruly asperated engine.There just the best.

yeah nothing beats it... except a tuned turbo engine

AWD i will find the charts for you. remember that most cars from the factory have small turbos and thats why they deliver power at lower rpm... in upoper rpm the turbos are " maxxed out" so to speak. with a larger turbo and some tuning you get power all the way to redline.

[bleh]

I agree with everything fox said.Who wants to wait for power to kick in at a certain rpm anyway?It should all be right there once u hit the gas.I also dont like the sound of forced induction engines.Nothing beats a highly tuned and refined natruly asperated engine.There just the best.

you say that because you love your i6, but tell me have you ever driven a turbo i6?

its seems theres a bit of miss information going on.... did anyone read my post? :roll: i think dj did, since hes posting like me.

[djfux69]

this is a stock rb26dett that is in a skyline. it is a 2.6 litre inline 6 twin turbo. it is also awd, so puts out significanlty less power to the ground. oh by the way the KW converted to HP is 303awhp

this is a vq35de. the 3.5 litre v6 that is in my 350z. it is a dyno before and after exhaust. obviously the stock number is what you want to look at.

this dyno is of a 2001 m coupe

[All Wheel Drive]

Thanks djfux.

[All Wheel Drive]

The Skyline curve does not help much as it has the x axis graduated in kph...

[djfux69]

it was a third gear pull. redline at 8,000 rpm. they started at the bottom of 3rd, so the line farthest to the right is the end of the gear since it is at the top speed of that gear.

[thepolarfoxqx]

i've driven a good number of well tuned forced aspirated cars, and in the end i still pick the naturally aspirated car. I'll have to get a dyno plot up sometime of the 318i. I had one done a bit ago, i'll have to dig it out, else have it re-done.

Forced aspiration has durability limitations, oil coolers are nice, but you still heat the oil up to temperatures it would otherwise never see in cooling a turbo. The idea is, if you are in the power band (say 4,500-6,800 on my 318i), you stab the gas, there is power there, no waiting for a turbo to get going, it's just there. I don't care what turbo it is, i have never seen a turbocharged car peak over 7,000 rpms ever. I may have seen one at 6,500 before, but usually they fall at 6 and below, the more you press the boost, the more this takes effect. This is because the cylenders cannot efficiently evacuate gas against the back pressure of the turbine at very high revs, there isn't enough time to force gas out against the added backpressure, thus putting a cap on the high end.

Turbos are not always a good answer to getting more power.

[LateNightCable]

Is anyone here familier with the Aerocharger? I'm not too much, but I always thought it was a pretty nifty concept, and a smart evolution on the turbocharger. To my knowledge, the only production vehicle equipped with this system is the VW Bus T4, but I have only read hear say.

I have read an account of the independant lubrication system acting up, and making the unit whistle very loudly as mileage increases, but I think the basic concept of a self contained turbo, with variable area turbine nozzles is a good one. Here are some of the features of the Aerocharger claimed by the company ...

* Variable Area Turbine Nozzles - For superior transient response without turbo-lag.

* Self Contained Lubrication System - For reliability, and ease of intalation. No lube or coolant lines.

* Low Friction Ball Bearings - Permit fast throttle response.

Website - www.aerocharger.com

[bleh]

I don't care what turbo it is, i have never seen a turbocharged car peak over 7,000 rpms ever. I may have seen one at 6,500 before, but usually they fall at 6 and below, the more you press the boost, the more this takes effect.

do you mean peak hp? if so then you didnt look at dj's posts.

This is because the cylenders cannot efficiently evacuate gas against the back pressure of the turbine at very high revs, there isn't enough time to force gas out against the added backpressure, thus putting a cap on the high end.

different cams, different head layout, a good manifold, downpipe and exhaust? this actually leads to my biggest problem with turbos, it completely changes any tuning techniques used with n/a tuning and is a bit more complex. it really is a different world of engineering even though the basics stay the same.

lnc, good research! i want one of those snails!!

[thepolarfoxqx]

the aerocharger has issues. Ford has used in recent turbodiesels that variable vein technology, with reasonable success. Turbo lag was reduced. The internal lubrication was that things big downfall, and true ball bearings have been in good turbos for a long time.

As for the dyno charts, only one of them peaked of 6,500.

And to get the best results in total power gain with a turbo, you usually choose to retard both your valve timing and your ignition/fuel timing. If you push it forward, you will minimize the effect of your turbo both up high (it won't drag) and down low (less torque).

My thought it why go throught all the trouble if you don't have to. You still haven't gotten rid of the issue of turbo lag and extreme under-hood temperatures.