Impressive, overly impressive results from my dyno today. Before the big numbers, it turns out I am overboosting my turbo, and that's bad. And that's probably helping the torque numbers a bit. The ECU is requesting no more than 21.5 PSI, but the turbo is making 23 PSI. not good. That must be resolved.
Let's review the numbers.
Stock
HP: 90
Torque: 155 ft-lb
Best numbers today
HP: 137.3
Torque: 272.6
That puts the torque right up there with the Porsche Cayman S. Hells yeah. And I'm still getting 40mpg around town.
12 comments:
How do you get the turbo to calm down?
installing a boost valve to shed excess boost.
What engine management are you using? Can't your tuner reduce the wastegate duty cycle mapping to hit target boost?
i have a Rocketchip tune. according to the logs, the ECU is requesting the correct boost, so i reckon something in the turbo is going wrong (sticky actuator?).
after i get the valve installed, i'll head back to the mechanic (who did everything but the ECU reprogramming) and have him check out the turbo.
Hi. I found your blog via JoeP's. Joe and I have been friends for 20 years now since we both started at Michelin at the same time out of college.
I don't know TDI tuning really at all, but I do a lot of turbo Subaru tuning. Your wastegate actuator certainly may be the culprit like you think. I also find though that off-the-shelf maps can vary in boost response from car to car. 1-3 psi variance at your boost levels is common in my world. The ECU requesting a target boost is not everything it needs, as there are other P&ID parameters that need to be right for the boost to be properly controlled. Sometimes if you send the logs to the company where you got the tune they can adjust it for you. Still... more likely a mechanical problem in your case.
Awesome torque BTW. I wonder if you have a bigger turbo if the power would come up a little more. Might not be worth the loss of low-end torque.
The WRS/STi cars I tune and build parts for are usually in the 250-400awhp (with similar ft-lb numbers at the wheels). Some of my parts have gone on fully-prepped cars that put out close to 600awhp too though on race gas. Pretty impressive for streetable 2.5l engines.
Matt, what do you think of the litchfield type-25?
Pyker, It's a nicely upgraded STi, but it has to be overpriced. I don't understand the need for a full $10k Cosworth engine for those power levels. The stock longblock is fine at 400bhp. With nothing more than a full exhaust and a tune any '04+ 2.5l STi can make 350bhp or more. Add a 20g turbo, injectors, and maybe a large intercooler and 450bhp is pretty easy. Back it off a little with a conservative tune and 400+bhp is fine with the stock engine. I guess it seems a little overengineered to me, but this is a good thing is some ways.
Yeah, but staying within reason doesn't get you a glowing review in Evo (ironic name in this instance). I think for these guys, it was a case of "if it's worth doing, it's worth overdoing!"
hey Matt, thanks for posting.
just this weekend, i developed a hole in my exhaust, so i'll be replacing the downpipe and cat with a 2.5" pipe, designed for my car, which is also bent for better airflow. (stock is 2" and has a near-crimp built into it).
if my still-original cat is clogged at all, which i think is possible, that could help explain the boost spikes. the better bend and high-flow cat should help that, even if it does end up collapsing to 2" at my muffler (i'll eventually put 2.5" all the way back). should help with my EGT's, as well.
a larger turbo is definitely the next step up, though for my car, what's typically recommended is a better intercooler and larger fuel pump. at that point, it'd also make sense to go up another nozzle size and of course get another tune.
a very popular turbo for TDIs is this Garrett 17/22 hybrid. from what i understand, it's not much of a sacrifice at lower RPMs.
but for now, i'm sticking with my stock turbo. i'm hoping it lasts another 2 years.
Yah, the Garrett turbos are better in a few ways - better turbine/compressor design, full ball bearing cartridges, etc. They generally are the preferred turbos in the Subie world too. I can see how you could get more power without losing low-end torque when upgrading to a Garrett.
Changes in downpipe design and quality can definitely affect boost response. So maybe wait and see on that.
But I don't see how a clogged cat. could increase your boost. Often backpressure has the opposite effect on a turbo - slower spool and lower boost. Diesels are unique in many ways, so I cannot be sure. But turbos are turbos.
Do your logs look at the engine's MAP sensor or are you relying on the boost gauge for your 23psi reading? Many boost gauges are surprisingly inaccurate.
I wouldn't be surprised if our 1.5psi variance is within the tolerance range of your tune.
For example... I loaded an off-the-shelf tune into a guy's car last week. It was supposed to be hitting about 16.5psi at our elevation (5000'-ish) but it was hitting more like 18.5psi. The ECU's "target" is 16.5psi but it just can't control it so it goes higher. I will have to adjust the max. duty cycles on the WG and maybe fool with the "turbo dynamics" parameters to get it back where it should be.
i did have some data logged and it does look like my gauge is reading accurate.
still deciding if i want to do the boost valve at the same time as the exhaust. probably should...
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