Boost at higher rpms.
05-21-2004, 01:22 AM
#1
Nordschleife Master
Thread Starter
Boost at higher rpms.
Do any of the turbo kits designs have a waste gate that adjusts with rpm?
Follow my line of thought, OK?
Detonation is caused by high combustion chamber temps. Such temps are caused by high dynamic CR. I think thats the term. Basicly the pressure that results after the changes caused by the intake, cams, etc.
Dynamic CR is the highest at peak torque. Higher the CR, higher the temps, and more likely detonation is.
OK, for a car like the 80-84 US cars, the torque curve falls off sigificantly as the RPM climbs. I guess this is because of the mild cams. If we had a blower that increased the boost toward the ends of the rpm band we could get sigificantly more power out of the engine at peak hp, w/o detonation problems at peak torque. Basicly, the blower would force the air into the engine to "make up" for the cams, exauste, etc, trying to choke the flow at the higher rpms.
The curve for the dynamic CR is not a geometric rate, so a centrifigual supercharger wouldn't match it to well. I'm guessing a electronic waste gate for a turbo?
Follow my line of thought, OK?
Detonation is caused by high combustion chamber temps. Such temps are caused by high dynamic CR. I think thats the term. Basicly the pressure that results after the changes caused by the intake, cams, etc.
Dynamic CR is the highest at peak torque. Higher the CR, higher the temps, and more likely detonation is.
OK, for a car like the 80-84 US cars, the torque curve falls off sigificantly as the RPM climbs. I guess this is because of the mild cams. If we had a blower that increased the boost toward the ends of the rpm band we could get sigificantly more power out of the engine at peak hp, w/o detonation problems at peak torque. Basicly, the blower would force the air into the engine to "make up" for the cams, exauste, etc, trying to choke the flow at the higher rpms.
The curve for the dynamic CR is not a geometric rate, so a centrifigual supercharger wouldn't match it to well. I'm guessing a electronic waste gate for a turbo?
05-21-2004, 02:02 AM
#3
Nordschleife Master
Thread Starter
I have one. A fiance actualy. She gets all the attention she can take, and the left over gets put into my hobies.
I'm studying to be a ChemE, and it's summer. My mind is always going, but now there is little for it to do. When it's not Thermo dynamic formula crap, it's often "how to get more power out of an Otto cycle engine." Namely the 4.7l engine in my car. Will I ever act on the ideas? Maybe one day, but not tomarow, as I'm kind broke. Besides, it's alought cheaper to make all my mistakes hypotheticaly.
I'm studying to be a ChemE, and it's summer. My mind is always going, but now there is little for it to do. When it's not Thermo dynamic formula crap, it's often "how to get more power out of an Otto cycle engine." Namely the 4.7l engine in my car. Will I ever act on the ideas? Maybe one day, but not tomarow, as I'm kind broke. Besides, it's alought cheaper to make all my mistakes hypotheticaly.
05-21-2004, 02:55 AM
#4
Rennlist Member
Well, the EGR valve functions to reduce combustion chamber temps and detonation. I doubt there's enough pressure there to overcome forced induction though. If there was, perhaps you could tie it in with a knock sensor, though I doubt it could react fast enough.
That's one of the reasons I'm so interested to see how one goes about SCing an OB...
That's one of the reasons I'm so interested to see how one goes about SCing an OB...
05-21-2004, 03:03 AM
#5
Nordschleife Master
Thread Starter
Just pipe the EGR valve into the car on the intake side of the blower, but after the AFM/MAF. You'll have to relocate the AFM/MAF in the intake track. If you pull the feed for the EGR valve from before the turbine wheel, there will be plenty of pressure to push the exaust gases into the intake tract.
As for detonation control, how about useing a set of aftermarket anti-knock sensors, with an intercepter unit on the ignition. When the EGR valve is not engaged, the spark is retarded enough to save the engine. The spark timeing controled by an anti-knocking feed back loop, with no input as to the position of the EGR valve. When the EGR valve engages, the spark is advanced up to peak power. What do you think about that?
However, you'd have to do multipul dyno runs to see if the EGR valve would allow enough advance to make up for the power losed to it's displacement of burnable air in the intake charge.
As for detonation control, how about useing a set of aftermarket anti-knock sensors, with an intercepter unit on the ignition. When the EGR valve is not engaged, the spark is retarded enough to save the engine. The spark timeing controled by an anti-knocking feed back loop, with no input as to the position of the EGR valve. When the EGR valve engages, the spark is advanced up to peak power. What do you think about that?
However, you'd have to do multipul dyno runs to see if the EGR valve would allow enough advance to make up for the power losed to it's displacement of burnable air in the intake charge.
Last edited by ViribusUnits; 05-21-2004 at 03:29 AM.
05-21-2004, 03:17 AM
#6
Rennlist Member
Yah, there would definitely be a lot of experimenting to make it work right. probably more like 100 dyno runs, and lots of road time with a logger. I think that the plumbing that you suggest could work with a turbo... centrifugal would even be OK set up like you describe. I much prefer positive displacement FI though, and it would only take a couple of bits of carbon coming through the EGR to score up the rotors.
Building a filter for the EGR line would be an interesting challenge.... but I'm not even sure that's necessary.
But beyond the plumbing, I really don't see what you're getting at in your middle paragraph above. Both scenarios you describe would result in less than optimal power. I think the typical approach is to use the knock sensors to retard timing/increase fuel depending on the setup. Again, I'm just sort of keeping my eye on developments. I have many small details to attend to both on the car and elsewhere in my life before I go the SC route though, so it's easy for me to be patient. Others with far superior resources, experience, and free time than I are working on solutions.
Building a filter for the EGR line would be an interesting challenge.... but I'm not even sure that's necessary.
But beyond the plumbing, I really don't see what you're getting at in your middle paragraph above. Both scenarios you describe would result in less than optimal power. I think the typical approach is to use the knock sensors to retard timing/increase fuel depending on the setup. Again, I'm just sort of keeping my eye on developments. I have many small details to attend to both on the car and elsewhere in my life before I go the SC route though, so it's easy for me to be patient. Others with far superior resources, experience, and free time than I are working on solutions.
05-21-2004, 03:28 AM
#7
Nordschleife Master
Thread Starter
Well, with a boosted motor, you've got to control detonation some how. You can only lower the CR so far, and there isn't much that can be done to improve the 16v head. Plus, if your trying to maintain stock internals, there is nothing that can be done. Intercooling will only get you so far. If you want more power, you've got to do something.
The easyest way to control detonation is to retard the ignition timeing. The 16v distributer is fairly easy to modify. Also, companys like Summit raceing sell gobs of intercepter units that will retard the ignition timeing with boost, and advance it with vacuum. Finaly, a company called "safeguard" or something like that sells a aftermarket anti-knock unit. Basicly, you pick out anti-knock sensors for your car by the diamiter of the cylinders. You hook up the unit, and then carefuly adjust the unit to provide the right spark retard for your set up. It apperently works well on after market blown mustangs.
Another way is to pipe an EGR valve in. The EGR valve helps to prevent the detonation, and maybe you get to run more boost. However, EGR valves are not precision units. They vary under the conditions, so the spark retard required to keep the engine safe varries as well. As a result, I would think you'd need a unit like mentioned above to keep the engine safe.
Course, I could be al wrong.
However, my orgional question was can you increase the boost near peak hp, when the cams and intake are reduceing the dynamic compression. Basicly get the blower to make up for intake tract and cam inadquacys.
Man we're up late.
The easyest way to control detonation is to retard the ignition timeing. The 16v distributer is fairly easy to modify. Also, companys like Summit raceing sell gobs of intercepter units that will retard the ignition timeing with boost, and advance it with vacuum. Finaly, a company called "safeguard" or something like that sells a aftermarket anti-knock unit. Basicly, you pick out anti-knock sensors for your car by the diamiter of the cylinders. You hook up the unit, and then carefuly adjust the unit to provide the right spark retard for your set up. It apperently works well on after market blown mustangs.
Another way is to pipe an EGR valve in. The EGR valve helps to prevent the detonation, and maybe you get to run more boost. However, EGR valves are not precision units. They vary under the conditions, so the spark retard required to keep the engine safe varries as well. As a result, I would think you'd need a unit like mentioned above to keep the engine safe.
Course, I could be al wrong.
However, my orgional question was can you increase the boost near peak hp, when the cams and intake are reduceing the dynamic compression. Basicly get the blower to make up for intake tract and cam inadquacys.
Man we're up late.
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05-21-2004, 03:46 AM
#10
Rennlist Member
05-21-2004, 04:10 AM
#11
Nordschleife Master
Thread Starter
If you look at the dyno chart, you can see the torque tapering off after 5500 rpm. This IIRC, is similer to what happens on a normal S4, the torque tapers off after 5500 rpm.
Basicly, it seems to me like Andy's set up just moved the torque curve up about 100-200 ft*lb. This is a very good thing because the stock S4 or GT has a reletivly flat torque curve. It's hard to get a judge of the torque the engine is putting out below about 3k, because of the effects of the torque converter's multiplication, but the high end very clearly mimics the curve of a stock GT or S4.
However, us with the 83 US 16v cars are in a whole nother world. Our cars have much smaller valves, and **** poor cams to boot. Peak troque is 263 ft*lb according to the factory. At 5252 rpm, torque is around 234 ft*lb. That is a pretty sigificant fall, IMHO. Expecaly when you compare to the Euro S motor of the same year. Peak torque is 263 according to the factory, like the US car, but at peak hp, the engine is still putting around 260-265 ft/lb. This also hold true for the Euro S2s. That basicly means that the top end of the engine's torque curve is nearly perfectly flat on the Euros. Now they're tradeing away a bit of the bottom end, but that accounts for the Euro S wild ride one the cam comes in. Also you can compare it to a S4 or GT motor, who's torque curves are nearly flat because of the intake and 4 valve heads.
My belife is that the cam and intake limiting the torque as the engine get up in the revs. This falling torque curve limits the hp output. Now, if it is truely the cam that is reduceing the incomeing air, and servceing as a restriction, thus reduceing the boost that the cylinder sees, we could safely increase the boost at the mannafold at higher rpm, and force it past the valves, even at high rpms, w/o detonation problems. This away the cylinder "sees" the same amount of boost, no matter the engine rpm.
Or I could be all wrong. This is pure theory. I've never seen it in print, or in application, so I don't know.
If you look at John's thread from a while back, you can very clearly see a rise in torque as the turbos spin up, and then it peaks as the boost comes online, and you can then see a very clear fall as the engine's rpms rise. This mimics the 16v engines charts from the factory. You have to innore the "before the boost comes online" regions to draw the comparason. In that thread, I also belive he indicates that the cams are limiting his torque at high rpms, and that he might have more than a few ponys to gain by switching to a Euro S cam.
That thread:
https://rennlist.com/forums/showthre...o&pagenumber=2
Basicly, it seems to me like Andy's set up just moved the torque curve up about 100-200 ft*lb. This is a very good thing because the stock S4 or GT has a reletivly flat torque curve. It's hard to get a judge of the torque the engine is putting out below about 3k, because of the effects of the torque converter's multiplication, but the high end very clearly mimics the curve of a stock GT or S4.
However, us with the 83 US 16v cars are in a whole nother world. Our cars have much smaller valves, and **** poor cams to boot. Peak troque is 263 ft*lb according to the factory. At 5252 rpm, torque is around 234 ft*lb. That is a pretty sigificant fall, IMHO. Expecaly when you compare to the Euro S motor of the same year. Peak torque is 263 according to the factory, like the US car, but at peak hp, the engine is still putting around 260-265 ft/lb. This also hold true for the Euro S2s. That basicly means that the top end of the engine's torque curve is nearly perfectly flat on the Euros. Now they're tradeing away a bit of the bottom end, but that accounts for the Euro S wild ride one the cam comes in. Also you can compare it to a S4 or GT motor, who's torque curves are nearly flat because of the intake and 4 valve heads.
My belife is that the cam and intake limiting the torque as the engine get up in the revs. This falling torque curve limits the hp output. Now, if it is truely the cam that is reduceing the incomeing air, and servceing as a restriction, thus reduceing the boost that the cylinder sees, we could safely increase the boost at the mannafold at higher rpm, and force it past the valves, even at high rpms, w/o detonation problems. This away the cylinder "sees" the same amount of boost, no matter the engine rpm.
Or I could be all wrong. This is pure theory. I've never seen it in print, or in application, so I don't know.
If you look at John's thread from a while back, you can very clearly see a rise in torque as the turbos spin up, and then it peaks as the boost comes online, and you can then see a very clear fall as the engine's rpms rise. This mimics the 16v engines charts from the factory. You have to innore the "before the boost comes online" regions to draw the comparason. In that thread, I also belive he indicates that the cams are limiting his torque at high rpms, and that he might have more than a few ponys to gain by switching to a Euro S cam.
That thread:
https://rennlist.com/forums/showthre...o&pagenumber=2
05-21-2004, 12:06 PM
#12
Rennlist Member
VU, take another look at Andy's Dyno sheet. What problem are you trying to solve? I don't see one, frankly. Sure the torque curve drops off, but by that time he's making 380RWHP and continues to do so to 6500 RPM. It seems to me if you want the better output above 5000RPM, the blower is the one to pick over the turbo. Problem solved!
05-21-2004, 02:50 PM
#13
Nordschleife Master
Thread Starter
Can we agree that more power is more better?
hp is calcuated like this
hp*rpm/5252 = hp
As you can see, the higher the torque, the higher the hp. IF you look between two cars, with the same red line, and peak troque, the faster one will be the one with the flatest torque curve.
If we could preserve the torque curve at the higer rpms, Andy would be makeing MORE power. Also, notice John's turbo set up. Once his tubos spin up, the resulting boost is constant. Therefor, once his turbo's spin up, the torque curve should be as flat as Andys. It's not.
If I'm correct that the cam timeing and valve sizes are chokeing the engine at higher rpms, we should be able to safely increase the boost at the higher rpms, and only the higher rpms, to get the air through the intake, past the valves, and into the cylinder, allowing a perfectly flat torque curve. This should be perfectly safe for the engine, because the cylinder only sees the boost after the valves have "restricted" it.
hp is calcuated like this
hp*rpm/5252 = hp
As you can see, the higher the torque, the higher the hp. IF you look between two cars, with the same red line, and peak troque, the faster one will be the one with the flatest torque curve.
If we could preserve the torque curve at the higer rpms, Andy would be makeing MORE power. Also, notice John's turbo set up. Once his tubos spin up, the resulting boost is constant. Therefor, once his turbo's spin up, the torque curve should be as flat as Andys. It's not.
If I'm correct that the cam timeing and valve sizes are chokeing the engine at higher rpms, we should be able to safely increase the boost at the higher rpms, and only the higher rpms, to get the air through the intake, past the valves, and into the cylinder, allowing a perfectly flat torque curve. This should be perfectly safe for the engine, because the cylinder only sees the boost after the valves have "restricted" it.
05-21-2004, 08:25 PM
#14
Rennlist Member
Originally posted by ViribusUnits
Can we agree that more power is more better?
Can we agree that more power is more better?
Anyway, it is not at all atypical for torque to drop off at higher RPM with any engine. Honestly, if I could put down numbers like Andy did I would not be the least bit concerned about the torque curve dropping off.
05-21-2004, 08:28 PM
#15
Nordschleife Master
Thread Starter
Ah, more power is better! This good.
You missed the point of the whole thing. I'm not saying there is anything wrong with Andy's set up, or John's. Infact, they're both putting down great numbers. I'm jeallous. However, I'd like to see how to make it better.
Ask yourself WHY the torque is dropping off. What is causeing it to drop off on just about every motor? Why is the torque curve shape of andy's engine so similer to that of the stock engine? Why is the same true of John's engine? Why are both of the engines curves so similer at diffrent boost levels?
Next, ask yourself what is the limiting factor of the amount of boost you can run. Is the limit at one rpm, or accrost the entire band, why? How can we increase the boost at other rpms to get more power, if the limit is only for a smallish section of it?
And finaly, is there anything we can do about the problems?
You missed the point of the whole thing. I'm not saying there is anything wrong with Andy's set up, or John's. Infact, they're both putting down great numbers. I'm jeallous. However, I'd like to see how to make it better.
Ask yourself WHY the torque is dropping off. What is causeing it to drop off on just about every motor? Why is the torque curve shape of andy's engine so similer to that of the stock engine? Why is the same true of John's engine? Why are both of the engines curves so similer at diffrent boost levels?
Next, ask yourself what is the limiting factor of the amount of boost you can run. Is the limit at one rpm, or accrost the entire band, why? How can we increase the boost at other rpms to get more power, if the limit is only for a smallish section of it?
And finaly, is there anything we can do about the problems?
