Forced Induction's FI91X report!

[Alky V6]

An intercooler is simply another tool in the methanol tuners toolbox that can be used to control the intial temperature of the intake and the rate of temperature rise of the intake. Intake temp rise and limits can be controlled by other tuning means (mentioned earlier) or the intercooler can be used in conjunction with the other tuning means to get at the desired result.

So what is the best setup? The best setup is the combination of any or all of the tuning methods available to the tuner that results in the target performance for the project.

 

[Alky V6]

The latest tuning sessions has rewarded me with a spool time of 1.7 seconds to develop 16 psi boost. The a/f is a little on the lean side during nitrous activation. It's level between 12.0:1 and 11.7:1. It's definitely starting to feel like a 220hp shot. I think the super cool mix of nitrous and alcohol is letting me get away with this lean mixture, although I've heard that this lean of an a/f with nitrous is possible in very controlled circumstances. I'm going to take it to the track and get a base line 60 foot before I start adding a little more fuel to the nitrous mix. Fuel is what makes the power, but I have to balance that with a proper exhaust gas temp to arrive at the best spool time.

135 kPa is the point where the spooling really starts to take off on its own. I will get you a time value from initial nitrous activation to 135 kPa. That seems to be the more important number to study. Another interesting figure to keep an eye on is the rpm at which certain boost levels are attained during spoolup. As I tune in the nitrous system, the time of spoolup is decreasing, but the relationship of boost level to rpm is staying pretty close. Maybe improving by about 5 kPa. For instance, before at 5200 rpm I would have 98 to 100 kPa. Now at 5200 rpm, I have 103 to 107 kPa. It's just that the rate at which the boost and rpm together rise is getting much quicker. My important target of 135 kPa is coming about at around 6,200 to 6,500 rpm. At that point the rpm and map almost straight line upward toward the stars.

I would imagine that a converter stall that gave me a stall speed of just over 6,000 rpm on the nitrous would give me a very quick spoolup.

 

[DCVING 6]

All things considered, where would you like to be timewise for spool up to the mentioned 16psi?

 

[Alky V6]

All things considered, where would you like to be timewise for spool up to the mentioned 16psi?

That's a very good question!!! It's one that I have been bouncing around.

If the spoolup comes in too quick, I could have traction issues. I'm still running 10.5" tires. With the spoolup more controlled over a period of time, the car has the chance to get out of the hole without breaking loose the tires. I think the answer to that question is going to involve traction only. I know the car will do 1.28 60 foots without traction loss, so I have a target to shoot for with this setup. If I had to guess what the 60 foot is with this latest tuneup, I would say 1.4s to 1.5s, which isn't that bad really.

What I did notice in front of the shop where I did my launch testing was that as the tuneup came in, the tires were laying down more rubber. An indication of how much tire spin I'm getting during the launch. This was on bare concrete though.

I also noticed no feeling of transition from boost and nitrous to boost only. The power transfer felt seemless. If there is any power loss, it's happening at a good time because when I hit 16 psi (turn off point for the nitrous) I'm in the middle of the 1-2 shift.

What has to be remembered is that even though the spoolup may be a little slower than the last turbo, the engine is on a 220hp shot for a longer period also. So during this ramp up of boost, there is also 220hp worth of nitrous helping things along at each psi step of boost rise, all the way to 16 psi. The pull feels scary in front of the shop.

 

[six shooter]

Any feeling how a slightly higher stall speed ( 400-500 rpm ) and a little less n20 might work? Would that change the way that the power was applied to those 10.5 tires?

 

[Alky V6]

Any feeling how a slightly higher stall speed ( 400-500 rpm ) and a little less n20 might work? Would that change the way that the power was applied to those 10.5 tires?

I would guess it would turn out to be a trade off. More rpm would increase exhaust volume, but decreasing nitrous would decrease exhaust volume.

 

[Dusty Bradford]

Any feeling how a slightly higher stall speed ( 400-500 rpm ) and a little less n20 might work? Would that change the way that the power was applied to those 10.5 tires?

The n20 will work better for spooling but with the power he will be making he could easily end up needing a looser converter to help those 10.5's.

 

[Alky V6]

Torque converter stall change

This is a good topic for discussion. The way I see it, since boost level is closely tied to the rpm, if I were to increase stall speed at the launch, nitrous hitting the same time as transbrake release, the rpm at launch would be higher and the boost ramp up will be quicker. The fact that the engine will be at a higher rpm alone means more horsepower. Add to that the nitrous and the quicker boost rise and I would think that you would be moving closer to the limits of traction for the 10.5s. On the top end, a looser converter might be a different story. Are my assumptions correct?

 

[Alky V6]

After doing a more detailed study of the last best datalog using the Data Log Lab software, I came up with some interesting figures.

T/C stall is between 4870 rpm and 5096 rpm. This occurs .504 secs. after nitrous activation. This is also with the car rolling out. From a staging rpm of 2552 the rpm rises sharply and noses over between these two rpm values. Just after nitrous activation (by 5235 rpm @ 99 kPa on the log) the O2 reading bounces off a rich reading of 10.40:1. This is the leanest value I've been able to get working on the initial nitrous hit region of the fuel map. It also feels very good. The O2 reading then quickly recovers to a stable a/f reading of 12.0:1 dropping slowly to 11.7:1 by 134 kPa.

The time lapse from initial nitrous hit to 134 kPa is 1.323 secs. As I mentioned before, once the map reaches a value of 134 kPa, the boost shoots up rather quickly.

At 145 kPa the fuel map reaches 'the wall'. At 172 kPa the wall drops to the new fuel curve with the nozzles supplying fuel now. Now this is interesting. The latest datalog showed a short lean spike as the map was passing over the drop of pulse width at the drop of the wall. This can only mean that the map is rising quicker than the fuel can start spraying out of the nozzles. There is a pretty fixed time value that's associated with the time that it takes for the fuel to purge all the air in the internal fuel rail and aux fuel feed line before fuel actually starts to spray out of the nozzles. The depth value of 'the wall' has to be timed with this purging time value. The lean spike in the datalog is showing me that I need to extend the depth of 'the wall' to make up for the fact that the map is rising quicker than before with the old T76. Very interesting. I've extended the depth of the wall from 172 kPa to 183 kPa. The time lapse from 145 kPa to 181 kPa is .218 seconds.

 

[Dusty Bradford]

Your looking at it from the engine side but with a lot of power you have to look at it from the tire side.

If you launch at 4000 rpm a looser converter will not be transfering as much power to the tire as a tight converter. The looser converter will couple at a later point in the rpm range. In a case where the tire can take everything you throw at it, a tight converter is a good thing. With more power than the tire can take, looser makes managing the power application much easier. The is a balancing point that has to be found for the best e.t and mph while launching the car properly.

Cars with big power often need 10% or more slip to make the trip down track. A 2000hp car won't make it past the gear change with a large rpm drop because it shocks the tires.

If Don runs into a situation where the n2o hit that it takes to spool the turbo is too much for the tires to handle, a looser converter can help.

 

[Alky V6]

I understand, Dusty. There comes a power level point where you have to switch over your focus from engine power to tire traction capacity. For consistency, such as bracket racing, a soft launch would not be a bad thing with 10.5 tires. Short shifting on the 1-2, catching the boost while it's still on the rise might control any traction loss issues during the 1-2 shift. What do you think? Or, simply just install the AMS1000 and start controlling the boost more precisely.

 

[S2V6RACER]

Don, you will not regret the choice for a AMS-1000. Cal is the man when it comes to these. You will need help from him so the customer support he offers you is worth every penny.


I can tell you if I didn't have one of these getting down the track would be much more work and I laughed when I read Dustys post above because that's what I just learned..... LOL

 

[Dusty Bradford]

You will need the AMS controller for sure. Your looking for the best possible e.t. aren't you or bracket racing??

Short shifting or a lower boost set-point while in 1st will help the tires or using the gear option in the AMS so that you swap to another boost amount at the gear change. The AMS will open a whole new set of tuning doors.

Launch boost, rpm and n2o hit will be where most of your headache will be. The n2o should allow you to leave with less rpm and still 60 foot like you need. The only issue I see is the amount of n2o you have said you need to spool the turbo. You will most likely be leaving more like a n2o car now than a turbo car. Controlling the boost rise and keeping the tires from smoking will be a challenge.

 

[Otto J]

At your current setup you should be far from being on the edge with a 10.5" tire.
Proper boost control will do wonders.

 

[Alky V6]

For a best ET, I figure another 30 hp on the nitrous hit will do the job of giving me a steady rising torque curve throughout the launch. The present nitrous hit should give me good consistent launches and a good top end charge to keep off the guys that like to come from behind on you. I was able to perform launches in front of the shop on unprepped concrete and not lose total traction. It may be the ticket for bracket racing.

You're right, Dusty. The car will be leaving like a nitrous car. The trick will be tuning the level of the nitrous hit to bring in the turbo at the right point. Not too early where cylinder pressures could get out of hand, and not so late that the torque curve starts to dip during the launch before the turbo can start taking over.

I'd like to get the turbo to that magical 135 kPa by 5500 to 5700 rpm. Right now it's reaching 135 kPa by 6100 to 6200 rpm.

 

[Underboost]

Looking Good Don. I can't wait to see her run.

 

[Drac0nic]

Some supercharged methanol engines lean out the mixture on the top end. This is done to maintain the target best power a/f ratio. Explanation. As the engine runs down the track, the heated, compressed air from the blower heat soaks the intake manifold. As the intake heat soaks, the charge air density becomes less. To maintain the target best power a/f ratio, the fuel must be leaned as the air density falls due to the heat soaking of the intake manifold. Basically, the intake manifold itself acts as a very, very small intercooler that becomes heat soaked rather quickly. Many tuning tricks can be employed to control the rate of the intake manifold heat soaking. Just one of those tricks happens to be the use of an intercooler to take away much of the heat that would normally heat soak the intake. With the rate of charge air heat increase hitting the intake manifold lessened, the rate of heat soak of the intake is also lessened. On a long run, the liquid intercooler would eventually heat soak and the rate of intake manifold heat soaking would sharply increase. That can be delayed by playing with different icing levels of the water for the intercooler. Remember. We don't want the intake too cold at the start of the run. But, if the intercooler isn't iced at the start of the run, then it isn't changing intake air temp beyond what it would be if there wasn't any intercooler at all. But, having the intercooler with ambient water temp will control the rate of intake manifold heat soaking. Basically, by running the intercooler, we have increased the very, very small intercooling capacity of the intake manifold.

I hope this makes sense.

We live in the era of electronics, tbh having the best of both worlds is child's play. You could probably take advantage of any "good" ECU like XFI, BS3 etc. to have an intercooler pump and/or solenoid valve switch on when temperatures exceed a certain point. You could even have a system with a secondary sensor that monitored the intake manifold temp specifically. This would allow you to run alcohol and ice water with virtually no penalty at all, and probalby significantly decrease the amount of ice (and consequently the weight) for a run.

 

[Alky V6]

We live in the era of electronics, tbh having the best of both worlds is child's play. You could probably take advantage of any "good" ECU like XFI, BS3 etc. to have an intercooler pump and/or solenoid valve switch on when temperatures exceed a certain point. You could even have a system with a secondary sensor that monitored the intake manifold temp specifically. This would allow you to run alcohol and ice water with virtually no penalty at all, and probalby significantly decrease the amount of ice (and consequently the weight) for a run.

Very good point. The intercooler tank could be iced, but the water flow would not be turned on until a certain temp or boost level was reached. A simple boost switch would be the easy to do.

 

[Red C5]

I just really want to say thank you for a very informative thread.

Peter

 

[Alky V6]

Looks like I'll need to employ other measures to get this turbo spooled. Nitrous alone isn't going to make it. A switch to a 1.0 a/r housing and a stall change are first on the list.