turbo lag??

[div]

i was running in a xsara rally car and i remarked that at high rpm my turbo was loosing some pressure and i released the accelerator and pushed it back right again and it started accelerating real fast and i want to know if that is turbo lag

 

[Jokerman]

Not really. Turbo lag is usually when you hit the accelerator and then it takes a few seconds afterwords for the turbo to spool up and add boost. In some cars with very large turbo's it can be very violent going from very poor yugo like acceleration to F1 neck snapping blast off. In some its very minor and isn't much of an issue. Rally cars, especially the older ones do tend to have a bit of lag, but the fall off of boost is something i have noticed in alot of cars once you get past a certain rpm. Maybe a blow off/waste gate of some sort. If you want to get a good idea of what turbo lag is drive a full tuned escudo from a dead stop and from idle. Its really sad.

 

[div]

i tried that it takes like 10 sec to get to 8000 rmp and then it blast!!!!!!!into space !

 

[Frustrated Palm]

Or h*ll if you did it incorrectly ...

 

[halfracedrift]

Yeah.. its funny... in the 1000 - 4000 rpm range, the scudo seems like a dam beetle.. after 5000, SHIZAM! it litreally like..... blows off... hehe

 

[Frustrated Palm]

or blows up ...

 

[div]

but the things im speaking about aint turbo lag so what is it

 

[halfracedrift]

lmao. that too!
and, the thing about turbo boost lost
if anyone has knowledge about F1 cars (i have a lil ) they can explain it

the lost of turbo is overboost and there a lil thing that keeps the boost chambre (w/e it is) sealed
when the pressure gets to too much, that thing pops up, reducing your boost
so, the thing ur speakin of is a safety feature for the car, cuz if it boosts too much, it will explode
but don't worry, the lost of boost doesn't affect you that much, just remember to keep the rpm low (thats right, LOW) when ur goin uphill in a car that has that safety feature, the boost will be kept at the max,

 

[Sage]

This exactly why it's not only best to use a manual transmission, but also to watch what you're doing when using it. Autos will always shift right when it bumps up against the redline- With a manual, you can control exactly when you want to shift, and the shift points vary in cars. In most naturally aspirated cars, you shouldn't shift before you hit the redline, and depending on the car, you can go pretty far past it (for example, the Honda S2000 and NSX are well known for being able to rev 1,000-2,000 rpms past the redline), while in turbo cars, the shift points vary widely. Some turbo cars act like naturally aspirated cars in that you should shift in higher ranges, while some you need to shift pretty far before reaching the line... as an example, the Lancer that is used in the IA-1 license (I forgot what kind it is, but I think it's a Tommi something) drops turbo boost significantly as its rpms go higher, and thus I had to shift about 1,000 rpms before the redline.

Just experiment with things, and you'll be fine.

 

[halfracedrift]

but is what i said correct youthcycler?

 

[Sage]

To be honest, I have no clue! neon_duke might know, as might a few other older members, but I don't have enough experience with real-life cars to know.

 

[Race Idiot]

It's a shame they didn't put turbo lag in the game.

Actually it's probably better off without it. I have seen a video with Jeremy Clarkson (Topgear Presenter) driving an XJ220. He was driving it normaly (at low revs) then he put his foot down, the car took at least 3 seconds to start spooling up (Is that the right term) the turbo and then the car went.

Although I think it is common in older turbocharged cars.

Also rally cars have a system that stops turbo lag, all I can remember is that they nicknamed it bang-bang. This was because the cars engine backfires at low revs I think.

Ah! here we go, here is a good page explaining it!

http://www.rallycars.com/Cars/bangbang.html

 

[Jokerman]

Ya but that system (which dumps huge amounts of fuel into the engine to keep it fireing and then keeps the turbo going) will eat up a titanium exaust on one of those rally cars in ruffly 300km. Not exactly something that is destined for the street thats for sure.

 

[Race Idiot]

Yeah, mind you it said that they have developed other ways of doing this.

Mind you it said that the turbo heats up from 800c to like 1100c

Although I had a magazine with a heavily modified escort cosworth that was fitted with that system, although he probably used group N or A parts.

Mind you I wouldn't want to pay for a new exaust every few weeks or so.

 

[ving]

**sigh**
NA tuning is alot more hastle free

 

[Race Idiot]

But the best way to go with small displacement engines is turbo.

You can get up to 600bhp out a YB cosworth 4cyl with the right mods and a turbo.

 

[Hell Spawn]

I've got the vid of the XJ220, at 4k revs the car is going like a tortoise, the turbos kick in and in a matter of milliseconds the car is at 130mph. Now this is turbo lag!

Halfracedrift wrote "the lost of turbo is overboost and there a lil thing that keeps the boost chambre (w/e it is) sealed
when the pressure gets to too much, that thing pops up". This device is called a dump valve and expelse the built up air pressure into the exhaust manifold. Thats where the 'puff' sound comes from when the car de-accelerates.

 

[Race Idiot]

Originally posted by Hell Spawn
I've got the vid of the XJ220, at 4k revs the car is going like a tortoise, the turbos kick in and in a matter of milliseconds the car is at 130mph. Now this is turbo lag!

Yeah I used to have the videotape, it had the early prototype speed12, the GT40 modified for tall people and they destroyed a 911, by dropping onto a caravan.

 

[Hell Spawn]

The GT43, hehe. I like the porche destruction. If the germans had this in WW2 and attached a gun to it, they may have won the war

 

[Race Idiot]

Yeah he drove the thing into the wall and the wall collapsed.

 

[Hell Spawn]

I can't remeber but is this the one with the Jag whatdayacallit. He accelerates and the rear of the car decides to overtake the front

 

[Race Idiot]

You mean the car that was first made to be the XJ220 but it handled like crap and he hit the camera?

 

[Hell Spawn]

yeah

 

[TingBoy]

Originally posted by Race Idiot
Also rally cars have a system that stops turbo lag, all I can remember is that they nicknamed it bang-bang. This was because the cars engine backfires at low revs I think.

I think it's called the misfiring system

 

[Race Idiot]

Nope, it is bang bang or ALS.

http://www.rallycars.com/Cars/bangbang.html

 

[GilesGuthrie]

Originally posted by div
i was running in a xsara rally car and i remarked that at high rpm my turbo was loosing some pressure and i released the accelerator and pushed it back right again and it started accelerating real fast and i want to know if that is turbo lag

No, it's not turbo lag.

What causes it is that the turbo is simply spinning too fast. This is NOT the same as overboost. Overboost is where the turbo is producing more boost than the engine can deal with (in which case serious damage to the engine internals will occur). To protect against this, a wastegate (not a dump valve) is fitted. A wastegate is a gate that opens allowing excess boost to be vented to the atmosphere. This produces a very high-pitched whistle, not the exhaling hiss that you hear when the accelerator is released.

Before going back to the boost fall-off, I'll just talk about the dump (or blow-off) valve and anti-lag.

Dump valves work in concert with the throttle. When the throttle is closed, the dump valve takes the boost currently being produced, and recycles it by feeding it into the exhaust side of the turbo. In this way, the boost keeps the turbo spinning, and reduces the lag from the turbo respooling once the throttle is reopened. Anti-lag systems in rally cars do this by (as Jokerman correctly says) dumping fuel into the exhaust manifold. This burns on the hot manifold, causing the exhaust pressure to be retained. It's also why you get the popping and banging, which occurs with each discrete addition of fuel to the manifold.

The boost fall-off is due to the aerodynamics within the turbo chamber. Put simply, the turbo has gone supersonic. As the turbo spins faster and faster, the outer edges of the blades begin to travel faster than the speed of sound. This causes sonic shocks within the chamber, which disrupt the airflow. Because the airflow is so critical, any disruption will cause a decrease in the pressure of the intake charge, and that will cause a loss of boost pressure.

Incidentally, this is also how restrictor plates work on racing cars. Basically, a plate with a hole of the dimension specified is inserted into the intake manifold. Below a certain intake pressure, air flows smoothly through the hole in the plate. Above that pressure, the airflow is disrupted and power is reduced.

 

[div]

wowowo excellant thats was excellant

 

[TingBoy]

Originally posted by Race Idiot
Nope, it is bang bang or ALS.

http://www.rallycars.com/Cars/bangbang.html

http://www.northarc.com/~edkwon/turbo.html ^_^

 

[Der Alta]

To add a bit more to Giles' info.

The turbo lag is what added more presence to heel/toe racing. With large turbo's, the lag was sufficient to the point that when dropping into low revs for a corner, the turbo would lag as it was spooling up exiting the corner. What drivers would do was keep the engine RPM high, with their toe, apply the brakes with their heel, and operate their clutch with the other foot. This allowed for more power upon exit of the corner.

In real life, advances have virtually eliminated the need for this. With proper engineering, a car can run two smaller turbos, making the same Hp as one large Turbo. This set-up allows the turbo to spool quicker and rpovide boost at a quicker pace.

An additional concept to this is a small turbo and a large turbo. You get the small turbo to spoll for the intial power, and then the Large turbo takes over after it has spooled.

I'm not 100% certain of my accurate description. Hopefully I've opened the discussion up for others to add more to. AFter all, we're here to learn.

AO

 

[GilesGuthrie]

Originally posted by Der Alta
To add a bit more to Giles' info.

The turbo lag is what added more presence to heel/toe racing. With large turbo's, the lag was sufficient to the point that when dropping into low revs for a corner, the turbo would lag as it was spooling up exiting the corner. What drivers would do was keep the engine RPM high, with their toe, apply the brakes with their heel, and operate their clutch with the other foot. This allowed for more power upon exit of the corner.

In real life, advances have virtually eliminated the need for this. With proper engineering, a car can run two smaller turbos, making the same Hp as one large Turbo. This set-up allows the turbo to spool quicker and rpovide boost at a quicker pace.

An additional concept to this is a small turbo and a large turbo. You get the small turbo to spoll for the intial power, and then the Large turbo takes over after it has spooled.

I'm not 100% certain of my accurate description. Hopefully I've opened the discussion up for others to add more to. AFter all, we're here to learn.

AO

I think that heel & toe was more for dropping the clutch on a downshift, helping to bring the engine speed (i.e. the input plate on the clutch) up to the same level as the propshaft speed. This prevents the drive wheels from breaking traction, which can have serious consequences in a rear-drive car, particularly if you're turning at the time.

Examples of the small & large turbo cars AO refers to:
Porsche 959
Toyota Supra
Ferrari F40
Mitsubishi 3000GT/GTO