98 vs 99, Manual vs Automatic - turbo behavior question

413 Views 9 Replies 5 Participants Last post by Rally Man, 2 mo ago

_HighVoltage_

Discussion Starter · 2 mo ago

Hi all. I wanted to ask those who have had numerous P80s a question about turbo behavior and feel. I've had my 98 T5m for over ten years and I'm very used to how it drives. Last year, I bought a 99R Auto and it feels like a completely different animal.

I know that right off the bat there are some notable differences:

4.4 vs ME7 ecus
16T vs 18T (and different wastegate preload settings)
Manual vs Automatic

Okay, but when it comes to driving them, the T5m feels like an old school turbo car from the 80s: huge turbo lag as the boost builds. Every gear change, boost is lost because the throttle closes, and it starts over again (doh!). The result is that I can feel a push back in the seat as the turbo hits full boost. Feels good.

Now the 99R Auto - it feels like a NA motor almost. I never hear OR feel the turbo spool. It just constantly surges forward. Of course, because throttle stays open during gear changes, boost is never lost, so that kind of makes sense. But the car just doesn't FEEL as fast as the T5m.

The stopwatch disagrees. The 99R is actually faster than the 98T5m (because I'm not really abusing the clutch), but both are around the 7 second mark from 0-60. The T5m just feels more fun. Almost feels like boost increases in the 98 (from 0-10psi), and boost fades or stays about the same all the time on the 99 Auto.

Is what I'm experiencing pretty common? Or should I be feeling a more pronounced turbo spool in the 99R Auto as well?

I have a boost gauge in the 98, but not in the 99 (can't figure out a good way to mount one - I want to avoid the A-pillar mounts)

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_HighVoltage_

Discussion Starter · #3 · 2 mo ago

canigo5.0 said:
I don't have a ton of experience with the ME7 cars, but I might have a few suggestions for dialing in the '98.

First is play with the wastegate settings. This can make a huge difference. Tightening it up half a turn at a time can be noticeable and reduce turbo lag. I'm pretty sure stock pressure for the wastegate is 4psi, if you have a tool to check.

Also, two other possible things to help driveability on the '98 are replacing the throttle position sensors and the boost control solenoid. There's a youtube video somewhere on the throttle position sensor, and it shows how these sensors lose readings at certain points over time. He says you can clean them up with brake cleaner, but they are pretty cheap new so I just replaced it. This made a huge difference in my manual car, as the power came on more consistently and it was way easier to smoothly engage the clutch. The boost control solenoid is another one that seems to slowly fade out, instead of just dying. Replacing this solenoid with the newer Pierburg one, that has been suggested here many times (hopefully someone else remembers the part number) gave me a lot quicker turbo response in one car in particular, and again it's fairly cheap so it's easy reassurance that everything is dialed in.

For the boost gauge you can get a bluetooth plug-in for the OBDII and then use an app on your phone to read boost, as well as a bunch of other readings. Obviously this route does not give you a true built in gauge, but you can still check boost when you need to.

Thanks for the insights! To clarify - I'm not really complaining about the 98, I like the way it drives. But I might indeed take a look at the TPS - it's the one thing I've never checked. I've already changed TCV and vacuum lines. Wastegate I have not checked and I might do that in the future.

For the 99 - is the ME7 processor fast enough to provide semi-accurate live data such as boost readings? I know that the M4.4 and 4.3 are really slow and only provide readings every few seconds (hence why I have not messed with looking into the bluetooth route)

I'm thinking about modifying the coin holder area somehow to place a gauge there.

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_HighVoltage_

Discussion Starter · #5 · 2 mo ago

canigo5.0 said:
I had a '97 850R that the bluetooth readings seemed too delayed and weird to trust, but that might have been 4.3. On my '98 cars with the bluetooth there is a slight delay in the reading on the app, but it seems pretty accurate. As in, you feel the boost hit as you accelerate and then about half a second later you see the number spike on the app boost gauge. I have a vacuum boost gauge in one of my cars that I tested it with, and the overall numbers were the same, just with the app reading slightly delayed.

Interesting. I didn't think you can read boost values on 93-98 cars as they don't have a MAP sensor.

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_HighVoltage_

Discussion Starter · #9 · 2 mo ago

UT OLI said:
My Auto R (MY 2000 w/ stock 19T) behaves the same as yours. The Auto T5 has much more throw you in the back seat turbo boost. As Will says I think the 600LBS weight difference is a huge factor. It's like having 3 200lbs guys riding with you.

I've seen that number 600lbs thrown around a lot. But didn't someone prove (on a scaled) that it was more like 350-400lbs? Still, I get the point.

Had some free time this morning and decided to run a less-than-scientific experiment. Brought both cars to the same section of road and timed them from 50-70mph with an iPhone app that uses the GPS signal. I did several runs in each, just to account for any error in the GPS signal. With the S70 T5m, I just gunned it in 3rd gear from 45mph all the way to 70 (started early to account for boost buildup), and then did something similar with the 99 V70R auto - let it coast to 45 and then mash the throttle with the kickdown so that by the time it was at 50 the slushbox had already changed down. Average results:
S70 T5m 50-70mph: 3.7 seconds
V70R auto 50-70mph: 4.0 seconds

So yeah, slightly slower but barely noticeable. And yet, the way the power delivery feels is radically different, confirming something SwedeSpeed-ers have known since the early 2000s: manuals are more fun

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