9.281 @ 146.99

[turbobuick]

Chris. When you are trying different cams on the dyno, are you using matching exhaust headers with each different cam to take advantage of gas pressure pulse tuning? This is very critical with long duration/high overlap cams. The wrong pulse tuning with a long cam can be killer. The whole gas flow package should be looked at as one system. The exhaust headers that are typically used on the Buick V6 these days is absolutely horrible, from the stand point of pulse tuning. Small cams with little or no overlap are not hurt by bad pulse tuning. The story is vastly different when you start exploring larger cams. If you're trying to match a cam to your intake and exhaust manifolding, then that's one story. If you're looking for more HP, you will find it with larger cams, if you're willing to tune the rest of the engine to match the needs of the cam.

My understanding (which is very little) is "pulse tuning" for headers is good only for a very short and very specific rpm point. In addition the idea is to take advantage of the scavenge effect that occurs during camshaft overlap. The scavenging effect would work very well in a NA or even supercharged and NOS motor but it typically something you want to minimize in a turbo motor due to the backpressure in the exhaust.

I'm looking for a cam that will operate in an rpm range I need to run my motor which is determined by trap MPH and rpm along with TQ conv efficiency and rearend gearing. I also want a cam that is perfectly matched to my TQ conv which hopefully will be loose enough to spool an 88mm turbo. I have not found this "perfect" combo yet and from the testing we've done, I would say I actually have a pretty mis-matched combo that actually kinda works.

 

[turbobuick]

I checked out the site. The formula is very simplistic. It does not take into consideration tire growth. At 150 mph, the tire growth can be 5-8 percent. A pro stock application can be 10%. A top fuel application, 20%.


If you want to check out some top notch calculators, go to Performance Trends site.

I'm using it only to as a reference and to look for changes. The only real way is with a datalooger, which I should have this year.

Increasing tire growth is only going to help you eff. # anyway.

 

[turbobuick]

To answer your question, Chris. I have not dyno'd the engine or car. All the performance figures I've come up with have been calculated from 1/8 and 1/4 mile performance, along with matching sims to the performance indicated by the time slips. The estimated peak HP rpm for the cam I'm using is around 6,700 rpm. Even so, the engine's pull does not let up all the way to 8,100 rpm, even though the sim states hp should be dropping off after 7,200 rpm. This is accomplished with a relatively small valve head.

The fact is, this complete engine configuration was first done on an engine analyzing program. Every single specification of this engine was figured out first on a simulation program with all individual systems optimized with the heads limitations at the core.

You are absolutely right about long duration killing low to midrange torque. Hence, the use of torque in a bottle. Once you get the engine up on the cam (and headers) and boost to around 18 psi, the gates of hell open around you.

The track is the best way. With a turbo motor niether a chassis dyno or an engine dyno load the motor exactly like it does on the track. I had to make changes to the VE table for all three senerios. The engine dyno had higher VE #'s and the chassis dyno had lower ve #'s so IMO the engine dyno loaded the motor more and the dynojet loaded it less. I'm going to play with a mustang dyno next.

 

[Alky V6]

The track is the best way. With a turbo motor niether a chassis dyno or an engine dyno load the motor exactly like it does on the track. I had to make changes to the VE table for all three senerios. The engine dyno had higher VE #'s and the chassis dyno had lower ve #'s so IMO the engine dyno loaded the motor more and the dynojet loaded it less. I'm going to play with a mustang dyno next.

I have heard the same thing from dyno tuners. One paricular tuner would first tune a new engine on an engine dyno, then followed up after the engine was installed with some chassis dyno work. After that, he would have to retune the setup on the street. He ended up skipping the engine dyno procedure and starting on the chassis dyno, but always performs final tuning changes on the street or track. Nothing beats real world.

 

[Alky V6]

I'm using it only to as a reference and to look for changes. The only real way is with a datalooger, which I should have this year.

Increasing tire growth is only going to help you eff. # anyway.

That depends on how closely you're running the engine at max rpm (on the down slope of your hp curve) per mph.

 

[Alky V6]

My understanding (which is very little) is "pulse tuning" for headers is good only for a very short and very specific rpm point. In addition the idea is to take advantage of the scavenge effect that occurs during camshaft overlap. The scavenging effect would work very well in a NA or even supercharged and NOS motor but it typically something you want to minimize in a turbo motor due to the backpressure in the exhaust.

I'm looking for a cam that will operate in an rpm range I need to run my motor which is determined by trap MPH and rpm along with TQ conv efficiency and rearend gearing. I also want a cam that is perfectly matched to my TQ conv which hopefully will be loose enough to spool an 88mm turbo. I have not found this "perfect" combo yet and from the testing we've done, I would say I actually have a pretty mis-matched combo that actually kinda works.

Exhaust header pulse tuning can be effective through an rpm range of 2,500 to 2,800 rpm. The scavenging effect on a turbocharged engine is just as effective as with a N/A application. And, to an even higher degree, because the working pressures on both sides of the cylinder, and in the cylinder itself, are so much higher. If tuned exhaust had no effect on a turbocharged engine, then I guess some of the old Indy classes that used long tuned primaries with turbochargers weren't paying attention to their dyno data. Imagine spending all that money on R&D and ending up with the wrong set of exhaust headers. Shameful.

Learn from the people with the bottomless research and development funds.

Finding a torque converter that will allow a quick spool up and have adequate coupling when the engine comes on the turbo is not going to happen. What about ATI's lockup converter for the PG? Set the converter up with a high stall for good spoolup, then lock it up for the top end. Now that would be the best of both worlds. Better than a slipper clutch, maybe.

I think your going about matching your setup a little backwards. Granted, you've done a fantastic job with it, to this point. You should concentrate first on what rpm band you want or can afford to run the engine at, taking into consideration the breathing ability of the heads coupled with the bore and stroke spec, searching for the optimum air speed through the intake port. That should be your starting point. Then work everything else around that. Otherwise, you will just end up with countless compromises.

 

[turbobuick]

Exhaust header pulse tuning can be effective through an rpm range of 2,500 to 2,800 rpm. The scavenging effect on a turbocharged engine is just as effective as with a N/A application. And, to an even higher degree, because the working pressures on both sides of the cylinder, and in the cylinder itself, are so much higher. If tuned exhaust had no effect on a turbocharged engine, then I guess some of the old Indy classes that used long tuned primaries with turbochargers weren't paying attention to their dyno data. Imagine spending all that money on R&D and ending up with the wrong set of exhaust headers. ShamefulT.

My understanding of the scavenge effect in a NA application is to create a vacuum in the exhaust port so that during the overlap period between the intake and exhaust valves occurs the exiting exhaust gas will help to pull the incoming intake charge into the combustion chamber. Is this correct in your thinking? If so how can you take advantage of this when you have 1.5 to 2 times the amount of pressure in the exhaust port as you do in the intake port?

My understanding of header and exhaust design for a turbo application is that it is going to be significantly different than that of a NA application. The relationship between exhaust back pressure and the effect header design adn camshaft profile have on it, and how it affects perfromance, is something very little is known about and very little has been written. I also think this is an area that a better understanding of could net some pretty impressive gains in HP.

What I know? Exhaust gas velocity and exhaust pressure are important in determining header design. I've been told that in a combo similiar to mine going from a 1/2" primary to a 5/8" primary has decreased BP using the same basic header design. I do also know a set of Hooker headers make significantly more upper RPM hp than a typical ATR design. I do know to big of a primary or to large of a header design will hurt turbo spool up. I've been told by Terry Houston that equal length primary deisgn has no to little affect on a turbo motor, not sure about that myself.

Exactly how did you come up with your primary diamter adn length on the headers you built? What did you use in making that decision?

Not arguing just making conversation and trying to understand myself.

Learn from the people with the bottomless research and development funds.

Finding a torque converter that will allow a quick spool up and have adequate coupling when the engine comes on the turbo is not going to happen. What about ATI's lockup converter for the PG? Set the converter up with a high stall for good spoolup, then lock it up for the top end. Now that would be the best of both worlds. Better than a slipper clutch, maybe.

We have been successful with a 10" 3200 stall converter with less than 7% slip using a vsc controlled with a gen 7. We turn it on at 1500rpm and shut it off at 7 psi to fill the converter before we leave the line. I've thought about LU's but haven't seen anything I would consider using at this power level and that works with a th400. A PG just won't work well in my combo a 2.10 TH400 seems to be the ticket.

I think your going about matching your setup a little backwards. Granted, you've done a fantastic job with it, to this point. You should concentrate first on what rpm band you want or can afford to run the engine at, taking into consideration the breathing ability of the heads coupled with the bore and stroke spec, searching for the optimum air speed through the intake port. That should be your starting point. Then work everything else around that. Otherwise, you will just end up with countless compromises.

Not really, this is exactly what I was saying. We used the dyno for that very purpose which was to identify were the motor was making power and what the characteristics of the cam profile were. I have since been chasing gear and converter combos to get it right and I'm still not fully there and don't think I can get there with what is available so a new cam profile is being considered. We will see what we come up with in my next grind which will be cam #4 in this motor.

 

[Alky V6]

My understanding of the scavenge effect in a NA application is to create a vacuum in the exhaust port so that during the overlap period between the intake and exhaust valves occurs the exiting exhaust gas will help to pull the incoming intake charge into the combustion chamber. Is this correct in your thinking? If so how can you take advantage of this when you have 1.5 to 2 times the amount of pressure in the exhaust port as you do in the intake port?

My understanding of header and exhaust design for a turbo application is that it is going to be significantly different than that of a NA application. The relationship between exhaust back pressure and the effect header design adn camshaft profile have on it, and how it affects perfromance, is something very little is known about and very little has been written. I also think this is an area that a better understanding of could net some pretty impressive gains in HP.

What I know? Exhaust gas velocity and exhaust pressure are important in determining header design. I've been told that in a combo similiar to mine going from a 1/2" primary to a 5/8" primary has decreased BP using the same basic header design. I do also know a set of Hooker headers make significantly more upper RPM hp than a typical ATR design. I do know to big of a primary or to large of a header design will hurt turbo spool up. I've been told by Terry Houston that equal length primary deisgn has no to little affect on a turbo motor, not sure about that myself.

Exactly how did you come up with your primary diamter adn length on the headers you built? What did you use in making that decision?

Not arguing just making conversation and trying to understand myself.

No. This is great. An exchange of ideas can only help.
Let me start off with a quote out of Turbochargers by Hugh MacInnes, HP books. "After cylinder pressure drops below critical pressure, exhaust-manifold pressure will definitely affect the flow. Higher cylinder pressure of the turbocharged engine during the latter portion of the exhaust stroke will still require some crankshaft power.
When an engine is running at wide-open throttle with a well-matched high-efficiency turbocharger, intake-manifold pressure will be considerably higher than exhaust-manifold pressure. This intake-manifold pressure will drive the piston down during the intake stroke, reversing the process of the engine driving the gases out during the exhaust stroke.
During the overlap period when both valves are open, the higher intake-manifold pressure forces residual gases out of the clearance volume, scavenging the cylinder. Intake-manifold pressure as much as 10 psi higher than exhaust-manifold pressures have been measured on engines running at about 900 HP. Good scavenging can account for as much as 15% more power than calculated from the increase in manifold pressure of the naturally aspirated engine."

It isn't that you're looking for a vacuum pulse to help suck the intake gases through the clearance volume and scavenge exhaust gases. What you're looking for is a 'pressure differential'. On average, the exhaust system might have a higher pressure than the intake manifold, but if the exhaust piping is tuned to enhance and time the low pressure pulse to meet the exhaust port during overlap, you get your scavenging effect.

Every exhaust system has high and low pressure pulses, either timed to enhance engine output, or not.

We have been successful with a 10" 3200 stall converter with less than 7% slip using a vsc controlled with a gen 7. We turn it on at 1500rpm and shut it off at 7 psi to fill the converter before we leave the line. I've thought about LU's but haven't seen anything I would consider using at this power level and that works with a th400. A PG just won't work well in my combo a 2.10 TH400 seems to be the ticket.

Is your T/C stalling at 3200 with zero boost?

 

[Alky V6]

Another quote from the same book. "Valve Timing and Duration - A camshaft profile that favors a certain engine speed naturally aspirated will have the same tendency turbocharged."

 

[Alky V6]

Another good quote from the same book. This quote is from Jim Kinsler of Kinsler Fuel Injection. Intake and Exhaust Tuning - "One of the biggest misconceptions is that ram tuning is not important on a turbocharged engine. Through extensive testing, I've found that a turbocharged engine responds to a tuned inlet and exhaust system and large-port cylinder heads as much as a naturally aspirated engine. The engine also needs much more cam than most people think. Don't strangle the engine!"
"One of the best examples of this was a 2.0 liter BMW that Gary Knudsen at McLaren Engines developed for Can-Am racing. The engine produced 540 HP on gasoline with Mack air-to-air intercoolers and a simple log-type exhaust manifold."
"Gary replaced the log manifold with tuned headers and picked up 60 HP. When he adjusted the cam specs to take advantage of the better exhaust, the engine produced 640 HP on the dyno and 600 on track! When Gary installed the tuned headers, throttle responce also improved tremendously."

If you take a look at any successful turbocharged engine used in Indy or other types of racing, you will notice beautifully tuned intake and exhaust manifolding. These people wouldn't waste the money if there wasn't anything to it.

Do you need to have tuned intake and exhaust systems to do 9s and 8s? Absolutely not!
Do you need tuned intake and exhaust systems to help maximize your engine configuration's output? Absolutely!

I would never have imagined that I would end up doing low 9s on just 22 pounds of boost and with small valve heads. The manifolds are doing something.

 

[Alky V6]

Exhaust side supercharging

I should add one other thought to this discussion of manifold pressure pulse tuning. I realize that intake to exhaust short circuiting during overlap is considered a big problem with turbocharged engines and things should be adjusted to minimize it. I whole heartedly agree with that idea, except in the case where the manifolding has been tuned to take advantage of the short circuiting. Advantage of the short circuiting? Yes, advantage.

The whole idea of overlap is to expel as much trapped exhaust gases as possible to leave more room for a clean air/fuel charge for the next combustion cycle. The problem is, some of the next air/fuel charge ends up passing through to the exhaust system. In a turbocharged application, this will tend to cool the exhaust and slow the turbo down. In a bad case, the fuel in the exhaust manifold can explode violently or just burn and raise exhaust temps to dangerous levels.
Now we add a tuned exhaust system. Remember, all exhaust systems will have high and low pressure pulses, along with short durations of flow reversal. If the exhaust system is tuned properly, you will have a low pressure depression pulse meet the exhaust valve during overlap. The clearance volume will be better evacuated of exhaust gases and then some of the next air/fuel charge will begin to be sucked past the exhaust valve on its way down the exhaust piping. Then, just as the exhaust valve is closing, a high pressure pulse will be traveling towards the exhaust valve and will ram some of the air/fuel that made it past the exhaust valve back into the cylinder. This is exhaust side supercharging. Two cycle engines make use of this phenomenon all the time with elaborately designed exhaust pipes (expansion chambers). This is one of the big secrets of tuned exhaust systems.

 

[Alky V6]

I came across a very informative link on pressure pulse tuning.

A two-stroke

 

[Alky V6]

1984 Buick GN
Weight 3,337 lbs with driver
Moser 10 bolt rearend housing with 4.11 pro gears and spool. 75-140 Penn syn lube.
33 spline axles
One right side air bag @ 25 psi
Stock upper control arms
Stock modified lower control arms
Poly bushings
ATR rear sway bar. No sway bar up front.
Stock front suspension
Competition Engineering adjustable shocks up front. Off the shelf Monroe shocks in rear.
15x10 Aluma Stars with 28x10.5-15 MT slicks
15x4 Aluma Stars with 26x4.5-15 MT
7/16" wheel studs in front. 1/2" wheel studs in rear.
Stock brakes in front. Ford large drums in rear.
Moroso line lock
Adjustable proportioning valve
Residual pressure valve to the rear brakes
Manual dual master brake cylinder
Manual steering box from Flaming River
6 point roll cage. Tied to the body and frame. Designed so that body can be easily lifted and completely removed from the frame.
Fiberglass bumpers and hood
DRW designed and built X frame member to strengthen the lower control arm mounting points at the frame and to help control frame and body twist.
Stroud parachute
Stock firewall and dash in place

Correction: That would be a Moser 12 bolt rearend housing. Ooops.

 

[Alky V6]

Lean runaway with methanol

At idle and during decel, methanol has some characteristics that require mixture tuning totally backwards of what you would expect with gasoline. The learning experience was quite interesting.
Imagine tuning in your lower rpm and load sites, and you blip the throttle to check, out of gear, throttle responce. The engine rpm increases as you would expect after you hit the throttle, but the rpm doesn't come back down. In fact, as you're waiting there and checking your throttle linkage to make sure it didn't stick, the engine rpm begins to slowly increase. The engine is sitting there singing at 3,000+ rpm and the throttle is at idle setting. You decrease the throttle stop setting, but to no avail. The engine is defiant. You finally have to cut the ignition. Thank god the thing shuts down! WTF! I walk into the office, where Murl is sitting and I just sit in an empty chair with a puzzled look on my face. Murl could hear what was going on in the stall next door and asked if I was having a problem. "Hell yeah!", I said. "The idle just ran away on me." He calmly replied, "You're too lean. Richen it up." I came back with a slight tilt of the head, a raised eyebrow and a confused look on my face. Kinda like a puppy dog trying to understand.

With gas you would lean out your decel map regions so you wouldn't load up the engine. Try that with methanol and you end up with runaway. You have to richen those areas until the engine will return to idle after a blip of the throttle.

An interesting way of controlling idle speed using the mixture setting above and below the target idle VE map cell with methanol is to richen the cell that is at the higher rpm/lower map, next to your target idle cell. The richness here will tend to make the engine come down in rpm to your target idle cell. In the cell to the less rpm/higher map of your target idle cell, leaning the mixture here will tend to make the engine rpm increase back to your target idle VE map cell. Right off idle, and when dropping into gear, maintain the, out of gear, idle injector PW. As you increase engine load towards converter stall, start to steeply ramp up your PW, particularly as you approach stall. The PW will start to somewhat plateau at converter stall and PW will increase afterwards at a much slower ramp up.

 

[Alky V6]

An interesting way of controlling idle speed using the mixture setting above and below the target idle VE map cell with methanol is to richen the cell that is at the higher rpm/lower map, next to your target idle cell. The richness here will tend to make the engine come down in rpm to your target idle cell. In the cell to the less rpm/higher map of your target idle cell, leaning the mixture here will tend to make the engine rpm increase back to your target idle VE map cell.

I had to develop this technique to maintain a stable idle, because without it the engine idle would uncontrollably oscillate. Kind of like the idle oscillation you hear with blower engines sometimes. Even when using ISC. This technique also eliminated the need to use ignition advance or retard trickery to maintain a stable idle.

 

[Chevota]

Don- Thinking of trying a 76gtq on my 231. At what psi do you think that turbo becomes inefficient with your current valve size?

thanx - scott wile

 

[Alky V6]

Don- Thinking of trying a 76gtq on my 231. At what psi do you think that turbo becomes inefficient with your current valve size?

thanx - scott wile

I'm not familiar with the 76gtq. If you can tell me where I can find a compressor map for one, I'll take a look at it for you. I can tell you what I feel about the Turbonetics T76 (non-super).

This is by no means fact. I'm not an expert on turbochargers. I still have a lot to learn. I can tell you what I feel from my experiences with my setup. It's not really a matter of at what psi the T76 goes inefficient. It's at what cfm. I believe the limit is 1,300 to 1,350 cfm. At the right airflow, you could push the psi to 37. That 'right airflow' window is very small though.

Why don't you go with a bigger turbo? If your target is 8s, don't do a 76. Personally, I've been looking at the 91. It has a forgiving surge line for our small displacement as long as you don't try to spool her too quickly, and would put you at a good efficiency point at max rpm.

 

[Chevota]

I'm not familiar with the 76gtq. If you can tell me where I can find a compressor map for one, I'll take a look at it for you. I can tell you what I feel about the Turbonetics T76 (non-super).

This is by no means fact. I'm not an expert on turbochargers. I still have a lot to learn. I can tell you what I feel from my experiences with my setup. It's not really a matter of at what psi the T76 goes inefficient. It's at what cfm. I believe the limit is 1,300 to 1,350 cfm. At the right airflow, you could push the psi to 37. That 'right airflow' window is very small though.

Why don't you go with a bigger turbo? If your target is 8s, don't do a 76. Personally, I've been looking at the 91. It has a forgiving surge line for our small displacement as long as you don't try to spool her too quickly, and would put you at a good efficiency point at max rpm.

My limitation on turbo size is the ability to retain the stock style THDP. I figured a 76 is the max for stock style downpipes. Am I mistaken? I hope so!

 

[Alky V6]

My limitation on turbo size is the ability to retain the stock style THDP. I figured a 76 is the max for stock style downpipes. Am I mistaken? I hope so!

Me too! I would love to go to something with more flow without having to change my setup. Let me know if you come up with something.

 

[Alky V6]

Over the last few days, I've been looking over some compressor maps and the Garret GT4718 looks to be my dream turbocharger. The engine sim responded to it in a way that can't be ignored. With this turbocharger the true limiting factors for the engine will be the head flow and cylinder pressures.