Importance of ignition advance in high boost applications?

[forcefed86]

I’ve been snooping around the small engine boards and keep running into huge power being made with very little timing and very high boost. I thought it odd I’ve never seen low timing and much over 20psi in the larger V6-V8 engine community, but it’s very common to see high timing and low boost. I've even heard multiple "guru" buick racers claim anything less than 18* of timing is pointless. Yet the 2.0 liter guys are running negative timing numbers at peak torque and single digit timing numbers up top making incredible power per cubic inch.


For example…
There are currently several DSM (2.0 4cyl) guys running 60mm holset hx40 turbos into the 37-43psi range and making 600-700 Awhp.(e85) None of them run over 18* of timing up top (usually around 16 or less). Some on 100% factory short blocks as well.

The few that I have spoken to run -5 to 8* at peak torque. For example this is the OEM timing map for an Evo 9.

As you can see timing is crazy low. Close friend runs this exact map on pump fuel (93) on his hx40 powered mitsubishi 2.3 liter at over 30psi of boost. He is well into the low 10 second range approx 550-575whp going by vehicle weight.

Personally I only run 18* at wot with my buick engine. I do however run 28-30psi (e85). Initially I tried 25* timing and would see knock right around 23-23 psi. I pulled timing and upped boost and my trap speed kept rising. I tried to push this farther, but I believe I'm having valve float at anything above 30psi in the upper revs. (110lb springs, factory valvetrain).

Is that only a "trick" that can be accomplished with newer/better designed heads and twin cam designs? Or does the smaller displacement in some way allow for the much higher manifold pressures?

I guess my question would be at what point will lowering timing and raising boost yield diminishing results? And if boost will make more power than timing, why don’t larger displacement guys run higher boost and lower timing?

 

[kidglok]

There are currently several DSM (2.0 4cyl) guys running 60mm holset hx40 turbos into the 37-43psi range and making 600-700 Awhp.(e85) None of them run over 18* of timing up top (usually around 16 or less). Some on 100% factory short blocks as well.

40psi to make 600hp?

 

[DR BOOST]

Is it possible to post a data log imposed on the timing map to see where the motor falls on the map.

 

[forcefed86]

40psi to make 600hp?

Manifold pressure is just resistance to flow. You can’t claim “X” amount of pressure yields “Y” amount of power. It will all vary with engine size and flow.

Is it possible to post a data log imposed on the timing map to see where the motor falls on the map.

Maybe, they are using ECM link though. I can't actually open the files without the program. That was just a screen shot. I'll see if I can get it.

 

[TurboBob]

Manifold pressure is just resistance to flow. You can’t claim “X” amount of pressure yields “Y” amount of power. It will all vary with engine size and flow.

Manifold pressure is also what fills the cylinder, so you can make some estimations. Manifold pressure, displacement, RPM, and efficiency (including any backpressure) and you have most of what you need to calculate power. The "efficiency" term is the tricky one.

Bob

 

[forcefed86]

Manifold pressure is also what fills the cylinder, so you can make some estimations. Manifold pressure, displacement, RPM, and efficiency (including any backpressure) and you have most of what you need to calculate power. The "efficiency" term is the tricky one.

Bob

Right, but where is the "cutoff point" for timing VS boost pressure. Seems like common since... the lower timing you run, the more boost you can add. At what point will you see diminishing returns? And does anyone really press it? Seems like very few take the approach of more boost and low timing. I'm talking about timing as seen in the graph above, not the typical 18* or so. If someone told me 10 years ago they were running 43lbs of boost and 1-9* timing from peak torque on up, I'd have laughed at them. Yet here we are... and people are doing it with great results.

 

[TurboBob]

The DOHC engines seem to be very different when it comes to timing. I believe that it has a lot to do with the centrally located spark plug. I.e. a short burn length in all directions. So they make power with less spark advance in general. That and their ports are huge in the cylinder head.

There have been lots of guys doing development over the years, and if there were an advantage to really low timing on our cars, I think we would know about it.

Bob

 

[TURBOPOWERED68]

The DOHC engines seem to be very different when it comes to timing. I believe that it has a lot to do with the centrally located spark plug. I.e. a short burn length in all directions. So they make power with less spark advance in general. That and their ports are huge in the cylinder head.

There have been lots of guys doing development over the years, and if there were an advantage to really low timing on our cars, I think we would know about it.

Bob

Maybe maybe not as some tuners have openly said in the past that they "wont give up all of their secrets"

 

[forcefed86]

Good point, comparing apples and oranges doesn't help. I was just wondering if any of the guys making good power out there went the low timing route. And if so, what kind of numbers they were running.

 

[tallor]

RPM and cylinder head design May also be a factor. I run a 1000cc 2 stroke snowmobile drag sled in the winter. Rpm 8900, rotary valve triple cylinder with timing of 25 degrees at 3000 rpm and then back it off up to 8000 with a final 13 degrees. Race gas engine 150 torque 260 hp.

 

[antiquettype]

First off boosted engines need less timing because the more dense the air charge the faster it burns since the molecules are closer. With that being said, having 5 degrees less timing when you have 10psi more boost has no where near the same effect as turning the timing back without boost. There is no downside to turning the timing down as the boost goes up as long as it is the amount the motor is asking for. You are not giving up power.
With all the tuners in the Buick community, I can assure you that the optimal timing for the motor is about where they are running them. There is so much data now that it isn't that difficult to zero in on.
If we ran our timing in the single digits even at 45psi it would not end with good results. Having too little timing can be as bad as too much if you go to extremes. Exhaust temps can get out of control with unburned fuel going out the exhaust valve.
I don't know a lot about motors, but I am pretty sure it has to do with combusion efficiency that dictates your timing advance. The faster combustion takes place the less you need. Some motors, like the bbc need lots of timing, and our Buicks not so much. Apparently these import motors have great cylinder head designs that promote very fast and efficient combustion that makes the motor require less timing.
The bottom line is, regardless of the motor or the boost pressure, they all want max cylinder pressure from combustion at the same piston position(going down). If you can get the cylinder pressure to come up just as the piston heads down and stay until after the rod is at a 90 with the crank you have really done good. That is where compression helps.

 

[Rafs-T-Type]

I haven't really read anything on here about people dropping their timing really low to up the boost, but I certainly would like someone to try it. All and all it seems like everyone has different experiences. Some people claim that E85 loves more timing while others say little to no gains are found advancing the timing after a certain point. From my readings though, from here and other turbo sites like dsm and supra forums, it does seem that most find more power from boost than timing.

 

[forcefed86]

Although not entirely correct, I always thought of timing as a burn speed control. The more the boost the faster and more uncontrolled the burn. Adding tons of fuel slows the burn, as does reducing timing. So technically the more boost you run the less timing you'll need for that optimal burn rate. I was thinking it seems like most of big boosted v8 crowd dumps in tons of fuel and run excessively rich AFR's and then run high timing. When it would be more efficient to run leaner AFRs and less timing. Most think the reason for dumping extra fuel was for a "cooling" effect. Researchers have found that's not the case at all. The extra fuel is just slowing the burn. It is very common for the DSM crowd to tune there motors to 12.5 or even 13:1 (on e85). I wouldn't suggest doing that on a Buick! This is just one more example of better head/combustion technology.

Of course, my theory is flawed. There will be a point where the timing will be to far retarded to allow detonation free gains. Each engine will have a different threshold for this. It seems the buick crowd agrees 18-21* is conservative and anything less seems to yield poor returns in hp/trap speeds etc. It has worked for me in the past, although I never tried anything lower than 17* on my very limited turbo tweak chip settings.

 

[antiquettype]

Although not entirely correct, I always thought of timing as a burn speed control. The more the boost the faster and more uncontrolled the burn. Adding tons of fuel slows the burn, as does reducing timing. So technically the more boost you run the less timing you'll need for that optimal burn rate. I was thinking it seems like most of big boosted v8 crowd dumps in tons of fuel and run excessively rich AFR's and then run high timing. When it would be more efficient to run leaner AFRs and less timing. Most think the reason for dumping extra fuel was for a "cooling" effect. Researchers have found that's not the case at all. The extra fuel is just slowing the burn. It is very common for the DSM crowd to tune there motors to 12.5 or even 13:1 (on e85). I wouldn't suggest doing that on a Buick! This is just one more example of better head/combustion technology.

Of course, my theory is flawed. There will be a point where the timing will be to far retarded to allow detonation free gains. Each engine will have a different threshold for this. It seems the buick crowd agrees 18-21* is conservative and anything less seems to yield poor returns in hp/trap speeds etc. It has worked for me in the past, although I never tried anything lower than 17* on my very limited turbo tweak chip settings.

Timing does not control the speed of the burn but when it starts. More fuel does not slow down the burn either but lowers the temperature of everything in the combustion chamber, especially the intake valve. Higher octane fuel slows the rate of combustion and is why you increase timing some with race fuel. I do not know any details of the turbo v8 guys tuning, but I would say if they run more timing than the Buick crowd I would guess it is not some special tuning tricks but simply what those motors need. The Buicks are old technology now but back in the day they were a very efficient chamber with a good head design compared to others, especially the stage 11 heads.

 

[bison]

It depends on the cylinder fill, rpm, and combustion chamber/CR, and alot of other small things. I remember a turbocharged mustang on the dyno where the owner did the timing table with this really low timing theory and it made about 700whp. Then after throwing some consevative for 93/alky 18-19* at it it picked up about 160whp. Still being on 93/alky and making 860whp. It eventually made over 900whp on 93/alky. Have a nice day. The cylinder fill is very important. If you have a 4 cylinder making 850hp@7200rpm and a v6 making 850hp@6400 rpm you can bet the 4 cylinder application will need considerably less timing to get it done. If you get greedy you get burned. The cylinder will get hot and rattle itself to death like a light switch. Usually fine through the 330' running like it never has before then as it approaches the 660' and hits 3rd that converter flash rpm will really get the cylinder hot and then it goes to hell.

 

[forcefed86]

Timing does not control the speed of the burn but when it starts. More fuel does not slow down the burn either but lowers the temperature of everything in the combustion chamber, especially the intake valve. Higher octane fuel slows the rate of combustion and is why you increase timing some with race fuel. I do not know any details of the turbo v8 guys tuning, but I would say if they run more timing than the Buick crowd I would guess it is not some special tuning tricks but simply what those motors need. The Buicks are old technology now but back in the day they were a very efficient chamber with a good head design compared to others, especially the stage 11 heads.

I'd have to disagree... Controlling the initial point of ignition also controls it's total overall burn rate, at the cost of efficiency. Also innovate has done many tests (as well as others) and measured total cc temps and pressures. They found more fuel does considerably slow ignition. They also found it has very little effect on the overall temperature in the cc. That is a common myth. OF course we are not talking about alcohol fuels, race gas, or any mix of the two.

 

[delcowizzid]

i run a later model 3800 like out of an 89ish lesabre or whatever they are called. LN3 is the engine designation N/a engine, 8-8.5:1 comp,roller cam, batch fire SD injection (factory delco ecu 1227808 or like a usa 1227165) with modified realtime tunable code.home made turbo kit at 14psi boost i only run 14 degrees max timing on 11.8-12:1 fuel ratio at 30-40*C inlet air temp in summer as measured in an inlet manifold runner to make 280rwkw or 380rwhp on our 95 octane which i think is your 93 octane in america. all street tuned watching the knock sensor for knock but our knock sensors are turned off after 3600rpm as engine noise overpowers the sensor so above that is all just seat of the pants to lazy to install knock ears LOL.when it hits full boost timing is only 8 degrees and ramps up at around 1.2 degrees every 400rpm untill it hits 14 degrees at 5600rpm then slowly levels off.its worked good at the track in a 3300lb car with 5 speed manual and 3.9 gears its gone 11.7@120mph in the 1/4 many times on second hand 26x9.5x15 hoosier quicktime pro dot tyres . the funniest thing is the engine had over 300000km (not a typo) on it before we cammed it and turboed it and has seen nothing but abuse 40+ drag passes 3-4 burnout competitions and lots of hard street driving and loves that low timing.next up we are going to fit a 3 bar map sensor and get up round 18-20psi which is where they normally start spitting out the stock gaskets people have found.if i keep pulling 1-1.5 degrees of timing per psi as is pretty normal practice to get in the ballpark ill be at 10 degrees max timing at 18psi but boost will allways win over timing, 4 psi of boost will gain more than 4 degrees of timing hands down.once we started getting 11's we switched to 110/130 avgas and only gave it an extra 1-1.5 degrees or so of timing and gained no time but trapped 0.1mph faster on the 1/4.we also had to lean it out a lot to get power back as the avgas dropped it 1 whole a/f point into 10.8:1ish ratios.
sorry for the long post and the fact it isnt a GN model buick engine but its close to it its just evolved a little

 

[bison]

The funny thing about this thread is that when considering the timing most havent even verified their actual timing . Imagine what is really happening when one thinks they are running 21* and they are really at 25*.

 

[Rafs-T-Type]

After much reading last night it seems that many of the E85 8 cyl guys put the car on the dyno and keep bumping up the timing until they don't see any more gains, then back it down a couple. The consensus seemed to be that the car will stop making power (or loose power) before detonation occurs. Again this info is for E85.

 

[SloGN]

The funny thing about this thread is that when considering the timing most havent even verified their actual timing . Imagine what is really happening when one thinks they are running 21* and they are really at 25*.

My thougts exactly........