Problem with the stage 4 turbo?

[inferno]

...

I knew my numbers werent spot on. Actualy i think peak torque occurs between 3500 and 5500 rpm, right? I dont doubt one bit you know more about it than me. Unfortunately I dont have the money or the exposure to be the kind of hands on car guy I'd like to be. In fact I've never even seen a Golf gti in person let alone whats under the hood. perhaps it would be more acurate to say the turbo is relativly large for the amount of boost it makes, which isn't much. But that may be untrue as well. My point was that just because the boost is droping that dosent mean power is droping. in fact, as the efficiency of the engine climbs with the revs, the ecu drops the boost presure to keep power output the same. But it does this to smooth out power delivery. people really hate peaky engines. i though this might have carried over, but the situation seems more severe than boost regulation. the 1.8t is one of the best turbo engines I've ever seen. In the perverbial sense of the word, of course.

 

[Shentar]

Could it be that the reason that the boost is falling back to zero is that the rivets and bolts on the diamond plate floorboards are coming off at that high rpm?

 

[AJP400]

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Hehe. Don't get me wrong mate, your figures were actually pretty accurate. It's just the fact that a K03 could be described as large that made me grin! Being fair you seem to have a good grip on turbocharging in general, so I won't patronise you.

Just for me, you and the real tuning freaks out there, here's a bit of info about my particular 1.8T engine (AEB code):

As standard (approx 7/8 psi boost pressure) the peak torque was 158.2 lb/ft at 3903 rpm.

After AmD Technik custom remap (14.7 psi - 1 bar boost pressure) the peak torque is now at 204.3 lb/ft at 4646 rpm.

The standard curve is quite flat as you say, but after turning the boost up it becomes more slanted, and increases steadily.

The torque drops off noticably after it's peak, as one would expect. This is because of the turbo losing efficiency, as we have discussed.

However, the power does not drop off until it hits 203.1 bhp at 5549 rpm. This is because revolutions per minute and torque have a direct correlation to the power. Even though the torque drops at 4646 rpm, the revs are still rising at this point. Therefore the power rises, but at a reduced rate, in correlation to the torque drop. And then the engine itself loses efficiency at peak power, so we change up a gear.

I could get even more technical, but I fear that I'm straying somewhat from the original discussion.

 

[LandoAWD]

How are you pulling these BHP #s?

 

[AJP400]

How are you pulling these BHP #s?

Do you mean how am I being so accurate with 203.1 bhp etc?

If so, I got a dyno (rolling-road) printout from the custom remapping session at AmD Technik. It shows power and torque before and after, peak figures etc, on a nice pair of graphs.

I even got an AmD sticker!!!

(I didn't put the sticker on the car, by the way!)

If you mean how is my car producing such 'high' bhp?

Then let me (briefly) explain. A custom remap involves reprogramming the ECU software that controls boost pressure, air:fuel ratio, igntion, timing etc.

On a natuarally aspirated car, the results are 'ok'. Lets say an extra 5 bhp for a 2 litre 4 pot.

However, on a turbocharged car, the results are well worth the money. Turn up the boost, play with the timing, and an extra 50 bhp is easy - even for just a 1.8 litre 4 pot.

 

[LandoAWD]

I have custom a EPROM in my ECU on the Laser. Timing advance, NLTS, stutterbox, fuel maps extended, yada, yada...I was wondering on the exactness.
A dyno would show WHP, no?

 

[JTSnooks]

Ok, I have a somewhat related question. Has anyone looked at the power/torque curves for any of the newer AMG mercedes? They always claim that peak torque is achieved from some crazy low number like 1500rpm all the way up until like 4500rpm or something. That would be really funny to see a long flat line like that in GT4, but I haven't had the chance to look. Can anyone confirm this, or do they look more like normal?

 

[AJP400]

I have custom a EPROM in my ECU on the Laser. Timing advance, NLTS, stutterbox, fuel maps extended, yada, yada...I was wondering on the exactness.
A dyno would show WHP, no?

Hehe. Yup, it shows that too!

Wheel hp is 151.1 bhp.

Sounds like some sweet software on your car. I'll try to upload some pics of mine - I'm sure you'll like the look.

 

[AJP400]

Ok, I have a somewhat related question. Has anyone looked at the power/torque curves for any of the newer AMG mercedes? They always claim that peak torque is achieved from some crazy low number like 1500rpm all the way up until like 4500rpm or something. That would be really funny to see a long flat line like that in GT4, but I haven't had the chance to look. Can anyone confirm this, or do they look more like normal?

I haven't looked, but I might check it out. I know the AMG SL 55 is a grunty beast in GT4, so yeah it's quite possible. You only see low-down torque like that on either a turbo-diesel, or a big throbbing V8! 👍

 

[LandoAWD]

Hehe. Yup, it shows that too!

Wheel hp is 151.1 bhp.

Sounds like some sweet software on your car. I'll try to upload some pics of mine - I'm sure you'll like the look.

Looks nice!

Mine isn't much of a looker, but it goes. 282WHP on a tank of bad gas and only 2 pulls.

 

[AJP400]

Looks nice!

Mine isn't much of a looker, but it goes. 282WHP on a tank of bad gas and only 2 pulls.

Sounds fast.

I'm having to sell mine though - moving into a new house soon and I need all the cash I can get.

I suppose the only time I'll be doing anything more than 140 mph nowadays is in a pretend car on GT4!!!

 

[LandoAWD]

It tends to do quite well around town.

Selling mine as well for the same reasons.

 

[inferno]

Could it be that the reason that the boost is falling back to zero is that the rivets and bolts on the diamond plate floorboards are coming off at that high rpm?

LOL.

The standard curve is quite flat as you say, but after turning the boost up it becomes more slanted, and increases steadily.

[BIGHEAD]Of course, in stock tune the turbo is running well within it's capacity. the closer you run to that capacity the longer it takes to reach full boost.[BIGHEAD]

However, the power does not drop off until it hits 203.1 bhp at 5549 rpm. This is because revolutions per minute and torque have a direct correlation to the power.

[BIGHEAD]Ahh yes, the magic number, 5250. You know what I'm talking about.[BIGHEAD]

[EDIT]

[smallhead]Sorry. Hey you stole my ... I had to do something. [smallhead]

[EDIT2]
On the S4. Nice.

I'm liking that laser too.

 

[extreme car]

I've tried Lancer Evo VII GT-A and the boost pressure dropping every 1000 Rpm strating from 4000 Rpm plus the boost won't fell off when I change gear which makes the car NA feeling car:tup:

 

[LandoAWD]

Boost falls off between shifts in a manual.

 

[Shentar]

Boost falls off between shifts in a manual.

That effect is limited with a BOV. Man I gotta get me one of those for my 300ZX Turbo.

 

[LandoAWD]

That effect is limited with a BOV. Man I gotta get me one of those for my 300ZX Turbo.

Not really. It keeps the compressor from backspinning, but most standard bearing turbos will still loose spool due to simple friction. A ball bearing turbo would have an easier time staying spooled as the resistance is less.

You SHOULD already have a BOV on your car. I can't think of ANY factory turbocharged applications in the last 10-15 years that didn't off the top of my head. There may be a couple, but it would suprise me if a 300zx was one.


Edit: Just noticed yours was an 86. I am unfamiliar with that motor as a whole.

 

[extreme car]

Boost falls off between shifts in a manual.

But when I tried in the game the boost doesn't come off it act like a NA car very2 fast reaction

 

[AJP400]

LOL.



[BIGHEAD]Of course, in stock tune the turbo is running well within it's capacity. the closer you run to that capacity the longer it takes to reach full boost.[BIGHEAD]



[BIGHEAD]Ahh yes, the magic number, 5250. You know what I'm talking about.[BIGHEAD]

[EDIT]

[smallhead]Sorry. Hey you stole my ... I had to do something. [smallhead]

[EDIT2]
On the S4. Nice.

I'm liking that laser too.

Hehe.

 

[GT_Belgium]

I had the same with an Audi TT (tourist) in GT3.. it sucked