I believe this is just total myth. Piping add nothing to the lag.SydneyJules wrote: The other function of turbo lag is the piping. The longer the piping the longer the spool up. What Greg is saying about the comp ratio is right- there's not enough "bang" in the engine without the boost for it to work properly, until there is compressor flow, and then they go go go.
But dont under estimate the piping side of things either. Ive said that my friend's 2002 with 6.5:1 static comp had no lag. at about 1/8th throttle in fifth gear it had 7psi boost. Perhaps the shorter gearing (4.27:1, and Getrag close ratio with a 1:1 5th) helped, but Im sure that all of his throttle response was due to the piping, because the comp ratio certainly didnt help.
Cam and ignition timing is way more important then intake volume, just think about how much air the engine sucks in at 3000rpm and then think about what an extra couple of litres will do. nothing
Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
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SydneyJules
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Greg Gordon
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The current fast Japaneese cars are designed from the outset to use high levels of boost. I don't work on them, so I can't say just how they do it but I suspect a lot of it in in the head design. Probably a very carefully shaped combustion chamber, good cooling flow through the head etc. Then there is the engine managment issue. Thier ECU's not only detect the slightest onset of detonation, they work proactively to prevent it. For example they start retarding the timing as soon as intake temps start to rise. This enables them to run the engines much closer to the edge of disaster and get away with a lot more boost.
A good example is the Chevy Cobalt Supercharged. It runs 12 psi on 9.5:1 compression. People are already bumping them up to 15-17 psi without problems. You won't get away with that on an Alfa V6. A Callaway GTV6 runs 10 psi with 7.6:1 compression. It's not unheard of to see Japaneese cars running 20 pounds of boost with 9:1 compression. I don't think any Alfa motor could do that. The ford Cobra 32 valve V8 seems to be able to handle incredible boost levels. There are many 20 psi cobras running 9:1 compression and putting out 800+ horsepower. Right now the 03'/04' Cobra is king of the street.
In short, your friend's BMW, like our Alfas was designed well before forced induction became commonplace. Even with great engine managment I doubt we will ever be able to use those Jap car levels of boost without totally redesigned heads. However all is not lost we can make up for a lot of that in displacement. With the old school BMW the 3430 big six or with an Alfa V6 punched out to 3.4 liters will have a 500-1500cc advantage over the hot jap cars.
A good example is the Chevy Cobalt Supercharged. It runs 12 psi on 9.5:1 compression. People are already bumping them up to 15-17 psi without problems. You won't get away with that on an Alfa V6. A Callaway GTV6 runs 10 psi with 7.6:1 compression. It's not unheard of to see Japaneese cars running 20 pounds of boost with 9:1 compression. I don't think any Alfa motor could do that. The ford Cobra 32 valve V8 seems to be able to handle incredible boost levels. There are many 20 psi cobras running 9:1 compression and putting out 800+ horsepower. Right now the 03'/04' Cobra is king of the street.
In short, your friend's BMW, like our Alfas was designed well before forced induction became commonplace. Even with great engine managment I doubt we will ever be able to use those Jap car levels of boost without totally redesigned heads. However all is not lost we can make up for a lot of that in displacement. With the old school BMW the 3430 big six or with an Alfa V6 punched out to 3.4 liters will have a 500-1500cc advantage over the hot jap cars.
What kind of turbo does your friend have? Did he make the manifold himself and if so, is it good?SydneyJules wrote:So you think its all in the comp ratio, comp/turbine sizing, and cams?
You do have a point with the 3k vs redline point... but why is an 8:1 car like an STi WRX running 1bar laggier than my friend's 6.5:1 8 SOHC 2002 running nearly 2 bar?
The only thing I've seen with the Subaru is that the boxer layout really destroys any possibility to have a decent manifold and that is really the base for a good lag-free turbo layout. If I'm not mistaken the subaru also has a pretty old turbo which won't help it's spool time.
Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
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SydneyJules
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Greg, if what you're saying is right, then you could be on to something in terms of re-working combustion chambers. From what I know of the japanese cars (Nissans, Toyotas,Subies) their factory tuning is always on the rich side at full load, especially the subarus. Most of the SR20 and RB25 factory engines ran 10psi into around 9:1, which isnt that extraordinary, so taking fuel out and advancing ignition made more power on them. There was nothing crash hot about their factory management systems- no knock detonators or anything like that. In fact, they all used hot wire airlfow metres. Still do, and dont know how any of them measured inlet temps- as far as I know, only top end brands go that far. Would like to say Alfa do, but I dont know. I know the BMW factory ECUs have good knock sensors in them.
Mats, the manifold is a nice tuned length one. Not sure of diameters.
The entire subaru piping set up is long and twisted. There is always a second between nailing the throttle and the boost actually pulling the car away. Even when you feed it on.
Anyway, Mats, interesting to find out how you think an ALfetta will outdo a 105... easier to drive on the edge? I had been told that what one of the cars doesnt do, the other does, and so on and so forth!?!?
Mats, the manifold is a nice tuned length one. Not sure of diameters.
The entire subaru piping set up is long and twisted. There is always a second between nailing the throttle and the boost actually pulling the car away. Even when you feed it on.
Anyway, Mats, interesting to find out how you think an ALfetta will outdo a 105... easier to drive on the edge? I had been told that what one of the cars doesnt do, the other does, and so on and so forth!?!?
Fixing it bit by bit....
I thought lag had a lot to do with the size of the turbine. The larger the turbine, the more gas it takes to spin it up and therefore the later it produces real boost (early Porsche 930). Of course a big turbine has less restriction and allows much more top end hp.
I'm not saying you can't create big boost with a small turbine but it will definitely run off its efficiency curve earlier.
Plenty of theories around and mine's another but I'm just a dumb n/a boy.
I'm not saying you can't create big boost with a small turbine but it will definitely run off its efficiency curve earlier.
Plenty of theories around and mine's another but I'm just a dumb n/a boy.
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SydneyJules
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Greg Gordon
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Jules, it is a big can of worms, and you are correct. The only way to figure this stuff out for sure it to try it.
Almost all fuel injected cars measure intake temps, including L-Jet GTV6s. The current crowd of fast G.M. cars (high end or not, even N.A. cars) adjust timing based on intake temps. This includes most SUV V8s, the Corvette, G.T.O. and Cobalt SS Supercharged. I know because I sell supercharger kits for G.M. cars. Not too sure about the Jap cars because I don't work on them but I suspect the EVO and STI do the same.
The WRX has a lot of turbo lag, at least the 2.0 227 hp version does. It's almost tricky to get the car rolling from a start because it's pretty weak just off idle. Once it's turbo spins up it's darn quick. Even when they are on boost my GTV6 beats them. Of course an EVO or STI would be a different story.
Almost all fuel injected cars measure intake temps, including L-Jet GTV6s. The current crowd of fast G.M. cars (high end or not, even N.A. cars) adjust timing based on intake temps. This includes most SUV V8s, the Corvette, G.T.O. and Cobalt SS Supercharged. I know because I sell supercharger kits for G.M. cars. Not too sure about the Jap cars because I don't work on them but I suspect the EVO and STI do the same.
The WRX has a lot of turbo lag, at least the 2.0 227 hp version does. It's almost tricky to get the car rolling from a start because it's pretty weak just off idle. Once it's turbo spins up it's darn quick. Even when they are on boost my GTV6 beats them. Of course an EVO or STI would be a different story.
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SydneyJules
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There is a lot of feelings and wanting around the 105 series but if you look at the pure fact the chassis is absolutely horrible in standard form, needs extensive rework to be fast.SydneyJules wrote: Anyway, Mats, interesting to find out how you think an ALfetta will outdo a 105... easier to drive on the edge? I had been told that what one of the cars doesnt do, the other does, and so on and so forth!?!?
A 116 chassis needs only springs and shocks all around and an adjustment to be fast.
Look at the rear roll centre in the rear suspension in the 105 or the motion ratio of the front spring.
Turbo spool is difficult, easiest is to divide it into two different parts, spooling from low revs and on-throttle response.
Jules, in my presentation thread there is a pic of a friend with a Holset HX35 on an Opel 1300 engine, that spools equally fast to my std 75 turbo from low revs...
Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
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la_strega_nera
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[quote="Mats]There is a lot of feelings and wanting around the 105 series but if you look at the pure fact the chassis is absolutely horrible in standard form, needs extensive rework to be fast.
A 116 chassis needs only springs and shocks all around and an adjustment to be fast.
Look at the rear roll centre in the rear suspension in the 105 or the motion ratio of the front spring. [/quote]
I've been spending a bit of time delving into suspension stuff with my ford, and from the stuff I've learnt designing a new front suspension for it (Using off the shelf "stock car" parts from the states) and from cutting up a '66 105 with a hacksaw and a 4" grinder, and owning 2 '77 GTVs (remember, i had that bare shell aswell) I have to say that theres *alot* that can be done to both chassis to improve the ride/handling combo.
The main point on motion ratio of the 105 front end is a problem shared with the 60's designed Falcon/Mustang platform, and means you wind up with insane spring rates and very short damper travels. This means *any* wear in the damper manifests itself as ratshit damping quality, and massive forces being loaded into the chassis by the spring. This leads to unnecessarily harsh ride to get decent handling. Then theres the cast steel lower arms, a problem shared by the 116 family cars.. very poor arm stiffness to unsprung weight ratio... those things have such a small section and weigh a tonne! Similar issue with the weight of the uppers, and that stupid bushing for the CCA needs to be replaced with poly or a spherical.
Then theres the camber curve on the 105s. Ball joint risers? Yes please! a longer upright to start with would be nicer though! And maybe a little smaller on the scrub radius?
The "3 link" alfa stuck under the back of the 105? who in their right mind puts the front roll centre at an almost acceptable height, and then makes the rear roll centre 18" off the ground, and locates it with a 50kg lump of cast steel? The rear end geometry would almost work if it had a watts or panhard instead!
Alfetta platform? Same problem with shit camber curves. Solutions? well, a knuckle riser like a 105 fixes the camber curve, but doesn't help the abominal front roll centre height. Upside down ball joints on the lower arms are the most expedient solution, they fix the camber curve *and* raise the roll centre to above the ground. Same goes for cutting/welding uprights. Wheel clearance can become a problem.
Raising the lower arms mounting point would help significantly, but would require ditching the torsion bars *and* a significant amount of custom fab work.
Caster change through soft bushings can be cured with the 105 CCA ball joint mod.
Those lower arms weigh a tonne. Some nice fabbed tubular arms would be nice, however for the really dedicated guy, you'd brace the upper shock mounts (tubular braces back to the centre of the firewall and across the two "towers"), ditch the stock arms and torsion bars, and run tubulars arms and coilovers. Might be something in a Coleman or Afco catalogue that'd do the lower arms.
Front Sway mounts crack with big bars, weld in re-inforcements help.
Alfetta rear end... well... The de dion could be lighter, the rear roll centre isn't bad but could be lower, and a spherical or poly bush in its front would be nice.
Of course, the de-dion is a bunch lighter than a 9" diff....
Ben
A 116 chassis needs only springs and shocks all around and an adjustment to be fast.
Look at the rear roll centre in the rear suspension in the 105 or the motion ratio of the front spring.
[/quote]I've been spending a bit of time delving into suspension stuff with my ford, and from the stuff I've learnt designing a new front suspension for it (Using off the shelf "stock car" parts from the states) and from cutting up a '66 105 with a hacksaw and a 4" grinder, and owning 2 '77 GTVs (remember, i had that bare shell aswell) I have to say that theres *alot* that can be done to both chassis to improve the ride/handling combo.
The main point on motion ratio of the 105 front end is a problem shared with the 60's designed Falcon/Mustang platform, and means you wind up with insane spring rates and very short damper travels. This means *any* wear in the damper manifests itself as ratshit damping quality, and massive forces being loaded into the chassis by the spring. This leads to unnecessarily harsh ride to get decent handling. Then theres the cast steel lower arms, a problem shared by the 116 family cars.. very poor arm stiffness to unsprung weight ratio... those things have such a small section and weigh a tonne! Similar issue with the weight of the uppers, and that stupid bushing for the CCA needs to be replaced with poly or a spherical.
Then theres the camber curve on the 105s. Ball joint risers? Yes please! a longer upright to start with would be nicer though! And maybe a little smaller on the scrub radius?
The "3 link" alfa stuck under the back of the 105? who in their right mind puts the front roll centre at an almost acceptable height, and then makes the rear roll centre 18" off the ground, and locates it with a 50kg lump of cast steel? The rear end geometry would almost work if it had a watts or panhard instead!
Alfetta platform? Same problem with shit camber curves. Solutions? well, a knuckle riser like a 105 fixes the camber curve, but doesn't help the abominal front roll centre height. Upside down ball joints on the lower arms are the most expedient solution, they fix the camber curve *and* raise the roll centre to above the ground. Same goes for cutting/welding uprights. Wheel clearance can become a problem.
Raising the lower arms mounting point would help significantly, but would require ditching the torsion bars *and* a significant amount of custom fab work.
Caster change through soft bushings can be cured with the 105 CCA ball joint mod.
Those lower arms weigh a tonne. Some nice fabbed tubular arms would be nice, however for the really dedicated guy, you'd brace the upper shock mounts (tubular braces back to the centre of the firewall and across the two "towers"), ditch the stock arms and torsion bars, and run tubulars arms and coilovers. Might be something in a Coleman or Afco catalogue that'd do the lower arms.
Front Sway mounts crack with big bars, weld in re-inforcements help.
Alfetta rear end... well... The de dion could be lighter, the rear roll centre isn't bad but could be lower, and a spherical or poly bush in its front would be nice.
Of course, the de-dion is a bunch lighter than a 9" diff....
Ben
Jeez... so much pointless dribble.
if you want to loose lag set it up right!
good control over your fuel and timing is everything, you can fix so much lag issues with the right engine management. something as simple as the right timing and fuel can induce a better hot burn = in quicker spool.
ball bearing turbo
quality intercooler cores
right diameter piping, as well as a short non restrictive path
but fuck, how deep do you want to go?
cam specs
turbo manifold design
turbo size specifics: housings, wheels front and back. (even ceramic)
exhaust flow
engine head flow
etc…
temperature being… engine, ambient, intercooler, compressed, etc all will effect it,
all turbo owners notice how fast a cold car spools or even on a frosty night.
point is all these things are WANK, you need to be in the ball park this will give you leniency in both ways to have the best of both places.
remember, nothing is ever perfect!
if you want to loose lag set it up right!
good control over your fuel and timing is everything, you can fix so much lag issues with the right engine management. something as simple as the right timing and fuel can induce a better hot burn = in quicker spool.
ball bearing turbo
quality intercooler cores
right diameter piping, as well as a short non restrictive path
but fuck, how deep do you want to go?
cam specs
turbo manifold design
turbo size specifics: housings, wheels front and back. (even ceramic)
exhaust flow
engine head flow
etc…
temperature being… engine, ambient, intercooler, compressed, etc all will effect it,
all turbo owners notice how fast a cold car spools or even on a frosty night.
point is all these things are WANK, you need to be in the ball park this will give you leniency in both ways to have the best of both places.
remember, nothing is ever perfect!
