16 replies to this topic

[ozzimark]

I decided to log some engine parameters from a 3rd gear pull to redline earlier, and turned up this:

RPM	TPS	Load	MAF	Ign
2820	83.5	47.7	107.47	14
3720	83.1	65.8	145.18	15
4500	82.7	77.2	163.27	15.5
5100	82.7	72.9	157.78	24.5

Notice how the airflow (shown in grams/sec there, 163 g/sec is about 21.6 lb/min) drops off from 4500rpmto 5100 rpm. I didn't back off on the throttle at all, boost is a constant 10psi last I checked, no creep or fading off, and there are no boost or vacuum leaks anywhere..

Does the VE of the stock setup really drop off so badly in the upper RPM that total airflow starts decreasing as the revs climb, or is there something seriously wrong with my car (plugged cat perhaps?) that I should attend to?

Does anyone else have any airflow data that they could compare to what I've found?

[Ellsworth]

Your load dropped off so the air flow followed. If you could increase the load you would see an increase in airflow.

[JCviggen]

Yes I have noticed this weird behaviour on my TT ECU and 3" MAF as well. At very high rpm's my load is dropping into the 60% area which makes no sense because boost is increasing all the time and so is airflow, yet the MAF starts to measure less at higher rpm's.

It seems inherent to the system.

[ozzimark]

Weird, even with your GT2871R? Does it seem to be a function of the maximum allowable airflow that you set to control the BCS/TCV? However, you state that airflow is still increasing with RPM for you.. I know your setup is far from stock, but that would certainly imply that I'm getting some aberrant results

Ellsworth, on 08 October 2009 - 01:40 AM, said:

Your load dropped off so the air flow followed. If you could increase the load you would see an increase in airflow.

See, I view it the other way around. Load is calculated from airflow and a few other things, so if I figure out why airflow is dropping, the load will stay up there, and I won't get such a depressing dropoff in torque/power in the upper end.

[Karl Buchka]

I don't really see what's so strange. Your turbo is falling out of it's efficiency range at higher RPM, so the compressor outlet temp rises. Higher temperature = lower density. Exhaust backpressure probably isn't helping your VE either.

[Ellsworth]

ozzimark, on 08 October 2009 - 10:42 AM, said:

Weird, even with your GT2871R? Does it seem to be a function of the maximum allowable airflow that you set to control the BCS/TCV? However, you state that airflow is still increasing with RPM for you.. I know your setup is far from stock, but that would certainly imply that I'm getting some aberrant results


See, I view it the other way around. Load is calculated from airflow and a few other things, so if I figure out why airflow is dropping, the load will stay up there, and I won't get such a depressing dropoff in torque/power in the upper end.

I would bet if you put it on a dyno you would see the torque peak around 4500 after that the load falls off and you are building horsepower, that's why you can run more timing from 4500-5000.

[ozzimark]

In an ideal world, peak torque would show up when airflow/rpm is a maximum and peak power would be where airflow is a maximum... and the response I feel when accelerating to high RPM supports that, since the torque and power REALLY falls off after 4500rpm, making it useless to go past 5k when I really want to get moving. I'll keep my eye out for the next local dyno day to give a solid answer to that question

Karl Buchka, on 08 October 2009 - 11:32 AM, said:

I don't really see what's so strange. Your turbo is falling out of it's efficiency range at higher RPM, so the compressor outlet temp rises. Higher temperature = lower density. Exhaust backpressure probably isn't helping your VE either.

At 163g/sec (0.16kg/sec) at 1.8 PR, the 16T has a bunch of room left before that should be occurring...

http://www.stealth31...04h-16t-raw.gif

It's actually in the middle of the peak efficiency right there

[Captain Bondo]

ozzimark, on 08 October 2009 - 02:41 PM, said:

In an ideal world, peak torque would show up when airflow/rpm is a maximum and peak power would be where airflow is a maximum... and the response I feel when accelerating to high RPM supports that, since the torque and power REALLY falls off after 4500rpm, making it useless to go past 5k when I really want to get moving. I'll keep my eye out for the next local dyno day to give a solid answer to that question



At 163g/sec (0.16kg/sec) at 1.8 PR, the 16T has a bunch of room left before that should be occurring...

http://www.stealth31...04h-16t-raw.gif

It's actually in the middle of the peak efficiency right there

That means pretty much nothing if the hotside is choking, you have some of the most scrawny camshafts ever designed, a cast iron exhaust manifold, and an intake tuned for low rpm. More things influence the powerband than just the compressor map as you probably realize. The turbo hotside has a bigger influence than the coldside imo.



Your airflow assumptions are correct, but assume optimal timing and AFR which are unlikely unless you have actually tuned the motor. The more appropriate reference is that torque will be highest where injector pulsewidth is widest, and horsepower will be highest where injector duty cycle is highest, again assuming a steady afr and appropriate timing.

[ozzimark]

Captain Bondo, on 08 October 2009 - 04:08 PM, said:

That means pretty much nothing if the hotside is choking

Which is entirely possible if say, the cat is plugged up. And yeah, I'm fairly familiar with the number of variables that play into airflow, even if the ICE course I took a while back was a waste of time.

I know that nothing on the intake side is the problem, plenty of flow left from the turbo, unless it's going bad, intercooler is fine, hoses are fine, tubing is fine, pretty new filter. The only other significant thing that could potentially be an issue is the camshaft timing, since I don't know where it's set to right now, and could be somewhat off from where I would be happiest with it.. same goes for the exhaust cam.

I guess I'll prioritize that 3" exhaust I've been slowly accumulating parts for... just need everything behind the downpipe If that helps, then cool, if not, I have more things I'd like to replace/change when I have the money for it.

[JCviggen]

ozzimark, on 08 October 2009 - 10:42 AM, said:

However, you state that airflow is still increasing with RPM for you..

Yes, actual airflow, not measured by the MAF. I am not monitoring the MAF rate exactly but I can see the trace log on the turbo tuner. It drops off in load after 6000rpm and at 7000+ rpm the situation becomes dire with the ECU seeing only 50% load even while holding 24psi at those revs.

The MAF signal drops while actual flow is anything but.

[EricF]

Captain Bondo, on 08 October 2009 - 04:08 PM, said:

That means pretty much nothing if the hotside is choking, you have some of the most scrawny camshafts ever designed, a cast iron exhaust manifold, and an intake tuned for low rpm. More things influence the powerband than just the compressor map as you probably realize. The turbo hotside has a bigger influence than the coldside imo.



Your airflow assumptions are correct, but assume optimal timing and AFR which are unlikely unless you have actually tuned the motor. The more appropriate reference is that torque will be highest where injector pulsewidth is widest, and horsepower will be highest where injector duty cycle is highest, again assuming a steady afr and appropriate timing.

The OP is on stock exhaust. From my personal experience with a lot of these mild setups, every car with stock exhaust will behave this way. With a nice exhaust, even with the TD04HL and stock manifolds, you'll be back to a freely rising powerband to 5500 or 6000, depending of course upon boost levels and boost fade. As for torque, that is going to continue to peak in the 3000s until your turbo's hot side flows better.

I have superimposed dyno charts from the same dyno of a 19T at 16 psi, and a T3/T04E 57 trim at 16 psi. They are really remarkably similar peak numbers-wise. It doesn't bear posting on here because the 19T dyno graph is basically trash due to boost fluctuations (it was ECU-controlled at the time, and would bounce between 14-17 psi).

What is interesting, is that the 19T still has over 200 wheel torque at the 6450 RPM limiter. The torque curve looks like a roller coaster due to the boost fluctuation, but if it were steady I think it would be peaking around 3500 RPM and be well over 300 (maybe 310-320). Power looks like it would peak at 5000-5500 somewhere. Though the peak power on that run was made at the limiter, I guess boost came back in at that point.

For comparison, the 57 trim T04E compressor (with the standard .63 AR T3 turbine housing and stage 3 T3 turbine wheel) has a torque peak at 4300-4500 RPM of ~265, and falls to around 175 wheel torque at 6500 RPM. This setup also had NA cams though IIRC. Power certainly does not fall off though with this turbo. It breaks up a bit higher in the RPM range, but certainly does not fall off much.

While the actual numbers are interesting because the TD04HL is actually a bit higher and certainly has more area under both curves at the same boost level, there are some big variables different despite being the same dyno. Air temp with the 19T was 88 degrees F, and with the 57 trim it was 114 degrees F. I hardly think the intercooler could be doing much with a mere fan pushing 114 degree air across it. Edit: the 57 trim's dyno run was also done on 15" drag radials at ~15 pounds of pressure. So slightly different gear ratio as well as a tangible bit more parasitic loss due to the softness.

Still, there is some value to the comparison. It shows that the TD04HL, albeit a small hot side, can still make power (and torque) higher in the rev range. It is still geared toward a peak torque in the 3000s, but it generally has a huge peak torque level and although it's falling off continuously thereafter, it still makes numbers. IMO it's underwhelming to drive, but it certainly moves a car well.

[Spanky]

JCviggen, on 08 October 2009 - 04:44 PM, said:

Yes, actual airflow, not measured by the MAF. I am not monitoring the MAF rate exactly but I can see the trace log on the turbo tuner. It drops off in load after 6000rpm and at 7000+ rpm the situation becomes dire with the ECU seeing only 50% load even while holding 24psi at those revs.

The MAF signal drops while actual flow is anything but.

Where are you measuring psi at?

[Captain Bondo]

While uncorking the exhaust will certainly help, IMO these engines still have a systemic issue. Ok Flamesuit on, I know how these little chats go.

The fact that a bigger hotside didn't make better number should start a whole bunch of sirens going.

What happens is the rpm where the turbo operates most efficiently got further away from where the motor makes good VE.

Notice how the few guys on here with bigger turbos often sometimes even make less torque than the 19t guys even though they make more hp?
Beause by the time the turbo is working efficently the motor VE has taken a dump.

The comparison is not terribly valid because the small turbo is working in synch with cams and manifolding that are efficient in the same operating range.

The bigger turbo only starts really working around the time the rest of the components are entering hibernation.

Yes with the small hotside they can still make some numbers at 6k, but again it's because everything is dropping off at the same time.

The motors are flat out grossly, grossly under cammed and until you fix it, you will not do a larger turbo much justice, everything else is still a weak link.

I have the same issue. VE on my motor in the range I want to run it at, sucks, and it's costing me a shitload of power.

EricF, on 08 October 2009 - 04:45 PM, said:

The OP is on stock exhaust. From my personal experience with a lot of these mild setups, every car with stock exhaust will behave this way. With a nice exhaust, even with the TD04HL and stock manifolds, you'll be back to a freely rising powerband to 5500 or 6000, depending of course upon boost levels and boost fade. As for torque, that is going to continue to peak in the 3000s until your turbo's hot side flows better.

I have superimposed dyno charts from the same dyno of a 19T at 16 psi, and a T3/T04E 57 trim at 16 psi. They are really remarkably similar peak numbers-wise. It doesn't bear posting on here because the 19T dyno graph is basically trash due to boost fluctuations (it was ECU-controlled at the time, and would bounce between 14-17 psi).

What is interesting, is that the 19T still has over 200 wheel torque at the 6450 RPM limiter. The torque curve looks like a roller coaster due to the boost fluctuation, but if it were steady I think it would be peaking around 3500 RPM and be well over 300 (maybe 310-320). Power looks like it would peak at 5000-5500 somewhere. Though the peak power on that run was made at the limiter, I guess boost came back in at that point.

For comparison, the 57 trim T04E compressor (with the standard .63 AR T3 turbine housing and stage 3 T3 turbine wheel) has a torque peak at 4300-4500 RPM of ~265, and falls to around 175 wheel torque at 6500 RPM. This setup also had NA cams though IIRC. Power certainly does not fall off though with this turbo. It breaks up a bit higher in the RPM range, but certainly does not fall off much.

While the actual numbers are interesting because the TD04HL is actually a bit higher and certainly has more area under both curves at the same boost level, there are some big variables different despite being the same dyno. Air temp with the 19T was 88 degrees F, and with the 57 trim it was 114 degrees F. I hardly think the intercooler could be doing much with a mere fan pushing 114 degree air across it. Edit: the 57 trim's dyno run was also done on 15" drag radials at ~15 pounds of pressure. So slightly different gear ratio as well as a tangible bit more parasitic loss due to the softness.

Still, there is some value to the comparison. It shows that the TD04HL, albeit a small hot side, can still make power (and torque) higher in the rev range. It is still geared toward a peak torque in the 3000s, but it generally has a huge peak torque level and although it's falling off continuously thereafter, it still makes numbers. IMO it's underwhelming to drive, but it certainly moves a car well.

[EricF]

Captain Bondo, on 08 October 2009 - 05:29 PM, said:

While uncorking the exhaust will certainly help, IMO these engines still have a systemic issue. Ok Flamesuit on, I know how these little chats go.

The fact that a bigger hotside didn't make better number should start a whole bunch of sirens going.

What happens is the rpm where the turbo operates most efficiently got further away from where the motor makes good VE.

Notice how the few guys on here with bigger turbos often sometimes even make less torque than the 19t guys even though they make more hp?
Beause by the time the turbo is working efficently the motor VE has taken a dump.

The comparison is not terribly valid because the small turbo is working in synch with cams and manifolding that are efficient in the same operating range.

The bigger turbo only starts really working around the time the rest of the components are entering hibernation.

Yes with the small hotside they can still make some numbers at 6k, but again it's because everything is dropping off at the same time.

The motors are flat out grossly, grossly under cammed and until you fix it, you will not do a larger turbo much justice, everything else is still a weak link.

I have the same issue. VE on my motor in the range I want to run it at, sucks, and it's costing me a shitload of power.

No need for the flamesuit, I agree totally.

I think this comes full circle though to why I always say "19T this" or "18T that" when folks here or on Tbricks have a more or less stock vehicle that they're looking to do a simple turbo upgrade on. All the manifolding, cam profiles, gear ratios, etc are all optimized for a hard midrange hit and a powerband that pretty much expends its usefulness by the stock redline.

The truth is that aside from a couple of mild upgrade turbos like the GT2871, K24, or a big 16G, there aren't many turbos outside of the TD04HL line that are a good match for the stock whiteblock's hardware setup (and that are worth the hassle to install).

As far as my setup, it probably would have made ~20 more WHP with better ambient and different tires. With a non-stock intercooler possibly even more. The run previous to that, I was running my street boost level of 23-24 psi, we lifted at the torque spike because it was getting lean on the dyno. At that point it was ~300 wheel torque and 270 whp (at 4700 RPM or so) Factor in another 1500 RPM and the above corrections for tire and ambient, and it was probably a solidly 300+ WHP setup. At a much happier boost level for the compressor of course.

The more bolt-on testing everyone does, the more we realize how critically all of the hardware components in a functioning engine need to work together in harmony. I think in your setup, some nice cams and some head work would catapult you violently to the next level. My current setup is probably sitting similarly (guessing around 300 whp at 18 psi, stock head, cams, manifolds, intercooler).

As it stands though, we can still make good power with what we have. We just are constantly working against certain components within our hardware setup. The results are very peaky and often narrow powerbands that can be underwhelming in their own ways. I'd still put my car together with a bigger turbo than necessary if given the choice, but only out of preference for the driving feel and knowing I can get a little bit more peak power than a turbo that contributes to the natural VE curve of the rest of my setup.

[shaun]

Captain Bondo, on 08 October 2009 - 05:29 PM, said:

While uncorking the exhaust will certainly help, IMO these engines still have a systemic issue. Ok Flamesuit on, I know how these little chats go.

The fact that a bigger hotside didn't make better number should start a whole bunch of sirens going.

What happens is the rpm where the turbo operates most efficiently got further away from where the motor makes good VE.

Notice how the few guys on here with bigger turbos often sometimes even make less torque than the 19t guys even though they make more hp?
Beause by the time the turbo is working efficently the motor VE has taken a dump.

The comparison is not terribly valid because the small turbo is working in synch with cams and manifolding that are efficient in the same operating range.

The bigger turbo only starts really working around the time the rest of the components are entering hibernation.

Yes with the small hotside they can still make some numbers at 6k, but again it's because everything is dropping off at the same time.

The motors are flat out grossly, grossly under cammed and until you fix it, you will not do a larger turbo much justice, everything else is still a weak link.

I have the same issue. VE on my motor in the range I want to run it at, sucks, and it's costing me a shitload of power.

I agree with all that, and I don't see it a grossly under anything. It was Volvos design intent. Volvo designed these motors to grunt, and grunt they do. As you state, the whole system: intercooler, throttle body, intake manifold, ports, valve size, cam geometry, turbo, exhaust manifold, exhaust, final drive ratio- what? 2.5/1 or whatever, the system is designed to make torque and utilize it. Gas velocity is much more important than ultimate gas flow given the design goal. I like it, volvo was ahead of the game with this setup, and Ford thinks enough of it that they put essentially the same set-up in the 2009 Focus RS 15 years after the t5 was put in production. The T-5 is a very solid piece of engineering IMO. One might have different goals for the motor, which will require the systemic changes physics demands.

[Captain Bondo]

Agreed. I suppose my point is that Volvo's design intent resulted in a motor that does not respond as well to the addition of large turbochargers as well as they might otherwise, and not as well as many other designs (Like Volvo's redblock DOHC motor, which has way more cam and way more port flow stock, and way more power potential stock-for-stock). If a set of 9.5-10mm, ~260 degree cams were available for these motors in a stock app, and especially if tube headers were available off the shelf, you'd see way more 400+ wheel horsepower whiteblocks, and a lot more 300+whp cars on stock (unbent) rods IMO.

FWIW this is just the usual crap I whine about all the time and never do much about.

[Spanky]

JCviggen, on 08 October 2009 - 04:44 PM, said:

Yes, actual airflow, not measured by the MAF. I am not monitoring the MAF rate exactly but I can see the trace log on the turbo tuner. It drops off in load after 6000rpm and at 7000+ rpm the situation becomes dire with the ECU seeing only 50% load even while holding 24psi at those revs.

The MAF signal drops while actual flow is anything but.

SPANKY, on 08 October 2009 - 05:18 PM, said:

Where are you measuring psi at?

I was curious if it was at the manifold or the turbo? It would only appear to be a anomaly if it was at the turbo. If the VE drops off as much as you guys say it does, then air velocity would become linear increasing psi at the manifold, while actual flow at the MAF would decrease.

Also their is two different diameters between the two, so pressure does not have to be the same to hold a specific pressure at the manifold.

I am probably wrong though. I do not even own a turbocharged volvo or a car for that matter. I just planned on infiltrating this forum for all the dirty threads, to see how high I could get my rating, and to piss chuck off