reducing spool times

[dwdsm]

I think this would make a good Newbie or turbo tech thread. Alot of people get into turbos to big and want to decrease the spool time. So lets make a list of things that help spool. I'll add a few and others can jump in. Just don't forget it's a give and take kinda thing. Some of these may cause lower topend.

Equal length manifold.
Bagging the turbine side of the turbo.
max timing pre spoolup then ramp down accordingly.
properly matched intercooler and short route piping.
Small/stock cams.

c'mon jump in.

 

[kahl23]

More displacement
Higher compression
Smaller A/R turbine housing
nitrous

 

[andy4g63]

Lower/retard/ the pre-spool timing and make it a little rich at the same time, at these same RPM's . A smaller TB would help too.

 

[soldave]

Lower/retard/ the pre-spool timing

max timing pre spoolup then ramp down accordingly.

So which one is it?

 

[T9S1i]

yeah really ive heard both before!!!

Im about to do some tuning on my s258 setup so i'd like to know!

 

[wishihadatalon]

retarded timing will make boost faster but advanced timing will give you better off boost power. To me the minute gains in spool time do not offset the dog feeling that I have seen with running the low timing.

 

[dwdsm]

Mine is maxed pre boost and I guess I should of logged before and after but it feels like it has more nuts off boost. Now I don't know if this is because of the motor making more off boost power or the boost comming on sooner. I guess after the insight it's more power from the motor off boost. So Good imput. If I get spunky I'll throw in the old map and compare the numbers with a max timing run.
I guess it's the same as...
*note* lighter drivetrain parts will increase accelaration but not spool.

Would a ported head/oversized valves decrease spool due to the higher volume?

 

[aero_sallee]

Variable A/R housing if you are ambitious and haven't picked a turbo yet.

 

[mach4g63t]

Check this thread out...

Spool Tuning

retarded timing will make boost faster but advanced timing will give you better off boost power. To me the minute gains in spool time do not offset the dog feeling that I have seen with running the low timing.

And Higher Compression pistons will help you feel a little better off-boost response, while allowing you to retard the timing for the pre-spool tuning mentioned in the link above. Sort of the best of both worlds?

 

[dwdsm]

Check this thread out...

Spool Tuning



And Higher Compression pistons will help you feel a little better off-boost response, while allowing you to retard the timing for the pre-spool tuning mentioned in the link above. Sort of the best of both worlds?

Your right I'll probally go 9:1 next time. Also less oil killing blowby

 

[dwdsm]

Variable A/R housing if you are ambitious and haven't picked a turbo yet.

That would be sick, If it was made. I don't know of such a thing...

 

[andy4g63]

max timing pre spoolup then ramp down accordingly.

So which one is it?

There is guy here on forums,1992awdlaser, he is a wiseman, he could explain much better, than me, but basically by retarding the timing, means igniting the fuel later and while burning exhaust valves opening. This is sort of how ANTI-LAG works.
Kind of the same with enrichening the AFR"s in pre-spool times too.

 

[DSMunknown]

Downshifting.

 

[2FoX2]

To go along with what dwdsm said, equal length manifold, combined with a high flow exhaust system will decrease the spool time.

 

[delta448]

Decreasing airflow restrictions at the compressor inlet (think MAFT, true CAI setup).
High-temp insulating exhaust wrap on the manifold.
External wastegate with an EBC.
A true divided turbine housing with the appropriate true divided manifold.
Removing exhaust restriction after the turbine; think no-cat, large dia. piping, DP cutout, etc.
Good results from a boost leak test.
Retarding the exhaust cam a couple of degrees.

 

[1992awdlaser]

What you want to do is retard the timing and add fuel pre-spool.

Retarding timing will make it spool faster. It does this because more of the heat from the power stroke goes into the exhaust manifold. I will try to explain each.

When timing is advanced the spark ignites the air/fuel mixture at a sooner point. This gives the mixture more time to burn in the cylinder. Most of the heat from this will be absorbed by the engine itself. The reason this makes more power is because the mixture has a longer time to burn before the piston reaches tdc. Since it has more time to burn it is going to make the pressure pushing down greater. This is where the exrta power comes from. More pressure downwards when the piston is at tdc. This is also why advancing timing can create knock or pre-ignition.

Retarding the timing makes the mixture start to burn closer to tdc. This will make less power since the mixture has less time to expand before the piston reaches tdc. Retarding will cause some of the mixture to be burning when the piston is moving down and when moving up on the exhaust stroke. Since the mixture burns later the heat has less time to be absorbed by the engine and as a result it will go into the exhaust manifold which will help spool the turbo. The mixture burning during the exhaust stroke also causes the turbo to spool sooner since the mixture is burning with the exhaust valves open. This is how antilag works, it retards timing so the mixture is burning when the exhaust valve is open.

When you add the fuel, the mixture will be burning longer since there is more fuel to burn. This will also cause the mixture to burn when the exhaust valves are open which makes the turbo spool faster. When the spark plug first goes off all the fuel doesn't burn right away. The fire spreads outward away from the spark plug. Since the flame spreads outward it takes time for all the fuel to burn. So, if you add fuel there is more fuel to burn which equals more time it takes to burn all of it. That translates into some of the fuel burning when the exhaust valves are open. This is another way of knowing how adding the fuel help.

 

[dwdsm]

What you want to do is retard the timing and add fuel pre-spool.

Retarding timing will make it spool faster. It does this because more of the heat from the power stroke goes into the exhaust manifold. I will try to explain each.

When timing is advanced the spark ignites the air/fuel mixture at a sooner point. This gives the mixture more time to burn in the cylinder. Most of the heat from this will be absorbed by the engine itself. The reason this makes more power is because the mixture has a longer time to burn before the piston reaches tdc. Since it has more time to burn it is going to make the pressure pushing down greater. This is where the exrta power comes from. More pressure downwards when the piston is at tdc. This is also why advancing timing can create knock or pre-ignition.

Retarding the timing makes the mixture start to burn closer to tdc. This will make less power since the mixture has less time to expand before the piston reaches tdc. Retarding will cause some of the mixture to be burning when the piston is moving down and when moving up on the exhaust stroke. Since the mixture burns later the heat has less time to be absorbed by the engine and as a result it will go into the exhaust manifold which will help spool the turbo. The mixture burning during the exhaust stroke also causes the turbo to spool sooner since the mixture is burning with the exhaust valves open. This is how antilag works, it retards timing so the mixture is burning when the exhaust valve is open.

When you add the fuel, the mixture will be burning longer since there is more fuel to burn. This will also cause the mixture to burn when the exhaust valves are open which makes the turbo spool faster. When the spark plug first goes off all the fuel doesn't burn right away. The fire spreads outward away from the spark plug. Since the flame spreads outward it takes time for all the fuel to burn. So, if you add fuel there is more fuel to burn which equals more time it takes to burn all of it. That translates into some of the fuel burning when the exhaust valves are open. This is another way of knowing how adding the fuel help.

Good imput thanks!

 

[crimsondragon]

What you want to do is retard the timing and add fuel pre-spool.

Retarding timing will make it spool faster. It does this because more of the heat from the power stroke goes into the exhaust manifold. I will try to explain each.

When timing is advanced the spark ignites the air/fuel mixture at a sooner point. This gives the mixture more time to burn in the cylinder. Most of the heat from this will be absorbed by the engine itself. The reason this makes more power is because the mixture has a longer time to burn before the piston reaches tdc. Since it has more time to burn it is going to make the pressure pushing down greater. This is where the exrta power comes from. More pressure downwards when the piston is at tdc. This is also why advancing timing can create knock or pre-ignition.

Retarding the timing makes the mixture start to burn closer to tdc. This will make less power since the mixture has less time to expand before the piston reaches tdc. Retarding will cause some of the mixture to be burning when the piston is moving down and when moving up on the exhaust stroke. Since the mixture burns later the heat has less time to be absorbed by the engine and as a result it will go into the exhaust manifold which will help spool the turbo. The mixture burning during the exhaust stroke also causes the turbo to spool sooner since the mixture is burning with the exhaust valves open. This is how antilag works, it retards timing so the mixture is burning when the exhaust valve is open.

When you add the fuel, the mixture will be burning longer since there is more fuel to burn. This will also cause the mixture to burn when the exhaust valves are open which makes the turbo spool faster. When the spark plug first goes off all the fuel doesn't burn right away. The fire spreads outward away from the spark plug. Since the flame spreads outward it takes time for all the fuel to burn. So, if you add fuel there is more fuel to burn which equals more time it takes to burn all of it. That translates into some of the fuel burning when the exhaust valves are open. This is another way of knowing how adding the fuel help.

Doesn't antilag also kill turbos? I rather keep the turbo lag if it means I'd have to replace my turbo in a few thousand miles.

 

[soldave]

Severe anti-lag can be dangerous for turbos for reasons I've read but which I've forgotten now (MR Alzheimer has a lot to answer for).

So when we talk about timing retardation, are you talking about a degree or 2 out of the whole lower rpm range of the timing map, or something more severe? Will post the current timing map up from my car this afternoon once I've downloaded it onto computer. I know one thing killing my spool at the moment to start with is the gain on my boost controller being turned right down because of a spiking problem I'm having.

 

[pneumo]

retarded timing will make boost faster but advanced timing will give you better off boost power. To me the minute gains in spool time do not offset the dog feeling that I have seen with running the low timing.

I agree. A few years ago I had knock issues with my car. I datalogged endlessly. I found that whenever knock came up, timing would naturally go down. If I was trying to hit boost at the same time, the knock would kill power, but boost would rise quickly. In other words with low timing I saw hi boost and no power.

My advice is to use mods to decrease spool, and use tuning to help the engine make power.

 

[T9S1i]

My advice is to use mods to decrease spool, and use tuning to help the engine make power.

so what are you saying dave? Use a big smim and cams to make gobs of top end and make up for the slow spool up with off boost timing advance to make the car more "peppy" off boost?

Or did I understand that wrong?

 

[pneumo]

so what are you saying dave? Use a big smim and cams to make gobs of top end and make up for the slow spool up with off boost timing advance to make the car more "peppy" off boost?

Or did I understand that wrong?

That'll work. Just don't expect to have great off boost power while big cams, big turbo, and smim take away low end power.

 

[turboglenn]

Downshifting.

Agreed, the best way to avoid lag and frustration is to just downshift to a low enough gear that you end up in an RPM range that will spool your turbo almost instantly. THat's what i do, then i run as much timing as i can for best power in off boost/transistion areas and run about 13.2 - 12.6 AFR's up to about 5-7psi, then a solid 12:1 - 11.9:1 after that diving to 11:1 flat by higher boost (above 20) and higher RPM's (above 4500) This has been the best balance i have found for good driving, no dead spots, good spool and a nice broad poiwerband.. I"m on e85 though, so my AFR's are where i like them (even ran similar on pump up to 14psi or so, then went richer to 11:1 right away after that, and up to 20psi or so on pump gas.

 

[aero_sallee]

That would be sick, If it was made. I don't know of such a thing...

It is. Its definitely not a bolt on, but makes a huge difference in spool while also helping topend. Currently its more work than most people are probably willing to put forth. With a custom manifold it would be much simpler and cleaner than the way I did it.

Here are some posts with some info about them.
http://www.dsmtuners.com/forums/turbo-system-tech/274459-holset-turbos-part-3-a-9.html#post151410859
http://www.dsmtuners.com/forums/turbo-system-tech/274459-holset-turbos-part-3-a-8.html#post151399725

 

[dwdsm]

I agree. A few years ago I had knock issues with my car. I datalogged endlessly. I found that whenever knock came up, timing would naturally go down. If I was trying to hit boost at the same time, the knock would kill power, but boost would rise quickly. In other words with low timing I saw hi boost and no power.

My advice is to use mods to decrease spool, and use tuning to help the engine make power.

This is what I do. I run max timing before boost and then slope it down according to the boost level. It helps with drivability and for things like autocrossing where sometimes on a 50 trim you will be running in vacume no matter what you do.
I agree power is a down shift away but there is the problem in autoX and road racing as being "inbetween gears". Plus on slow courses the car is between 1st and 2nd gear. Now there is a decision.. bog in 2nd or go into 1st to just run out of it in .2 seconds.