Update

[Dreamstate]

Props to DIY youtube repair videos.

I've become comfortable doing things that I previously didn't want to get into. This weekend I did tie rod ends, CV boots and control arm bushings on the TDi. The CV joint removal is what I wasn't looking forward to, but it wasn't so bad in the end.

[mushroom_curry]

Sweet. Link to DIY vids?

[Dreamstate]

This is the one I found to learn how the CV joint attached to the axle.



Most DIY vids just replaced the whole axle, I wanted to keep the factory axle and CV joints and just replace the boot.

[mushroom_curry]

Noob turbo question here...

If I have a tune for a 1.8T that's specific to a 440cc injector for example... and I run a frankenturbo on it one day, and a GT28RS another day, does the tune need to change?

Essentially, the tune is trying to maintain a specific air/fuel ratio, is it not? And if the ECU is able to read the boost, despite the turbo size, the tune should be able to handle it, right?

Please enlighten me!

[Dreamstate]

I'm with you, I don't understand why an upgraded turbo would need an ecu upgrade. The map sensor still works the same.
For some reason everybody does it. Marketing maybe? Or is it because you usually upgrade the injectors at the same time? Or is there something that changes that I don't understand either that requires an ecu flash?

[mushroom_curry]

One thing that a tune could likely govern is injector spray duration.

Now if the time the injector is spraying is limited by the window of time that the injector has to fire (RPM), then there still must be some wiggle room here to spray longer or shorter durations of time... although these would be very small changes.

SO unless the tune really focuses on the expected moment in time that boost builds in the RPM range, and then trims or expands injector spray time accordingly, then I can appreciate why there would be a different tune catered to a specific big turbo. However, in the K04 and GT28RS category, I would imagine the two are faiiiirly interchangeable. Not optimal, but it would all still work, except for maybe running a bit rich down low and some odd spikes through the power band where boost production differs.

I saw somewhere that some newer cars instead of using a chip have a tuning system that piggy-backs off the injectors to increase power? If this is achieved by managing injectors and say working within the limitations of time during a full engine cycle/rotation to up fuel volumes by a certain percentage, then this makes sense as a power increasing tactic.... even on an N/A vehicle.

Which, come to think of it, makes me wonder how much HP my VR6 is making on standalone with the current tune I have loaded... and how much a chip in an N/A setup really does to improve power via injector control (especially when the chip is a cam-specific one that considers valve timing).
Which, come to think of it, makes me wonder how much HP my VR6 is making on standalone with the current tune I have loaded... and how much a chip in an N/A setup really does to improve power via injector control (especially when the chip is a cam-specific one that considers valve timing).

[mushroom_curry]

I want to put 380cc injectors in my 1.8t (Audi TT units), but I still have the same old turbo.

My guess is that fuel injector timing is trimmed down low, based on air fuel, and then adjusted as you go through the RPM band.

Based on that guess actually, the ECU should be able to trim/lengthen fuel injector pulses as required based on air fuel.

[Dreamstate]

Your open loop state would go way out of whack if you change injectors without adjusting the ECU. Changing injectors would absolutely require a reflash.

One thing that you did on turbo retrofit cars in the earlier manual/mechanical tuning days did was use a rising rate fuel pressure regulator. My Corrado had this before I went to C2 software and then to the current SDS. If the injectors weren't too much larger than the originals, I could lower the base pressure of the regulator so that it would get the same quantity of fuel at idle and then fiddle with the rising rate as needed. Quick and dirty, but it worked for the most part.

[Maraschino Larry]

Haha yup... When I fed my DSM more fuel with 550cc injectors and a Walbro 255 high flow pump I "tuned" it with an Aeromotive adjustable FPR and a palm pilot with some crude data logging software leaning it out until it would start to knock, and then raising it up a touch. Quick and dirty it was, but I never blew it up and it seemed to make it go fastar. And I felt really cool.

[mushroom_curry]

Oh ya no I would only be going TT225 units because there's a local special on upgrading my Stage1 Revo tune to Stage2 for $20.

The tune requires a decat pipe and 380cc injectors.

Car feels such lack of low-end power, so hoping this mod helps with that since I granny shift at 3000rpm

[Dreamstate]

... And I felt really cool.

That's something the new stuff just doesn't give me the same excitement anymore. The 5 minute chip flash has taken the skill out of tuning. I mean sure, you don't break stuff as often and the tuning is bang on, but you're not pushing any personal boundaries or building skill either.

[mushroom_curry]

how did the rising rate regulators of yore work?

depends solely on vacuum to indicate throttle position? or was there an electronic component that tapped into the TPS?

[Dreamstate]

Much like a standard fuel pressure regulator, there's an internal spring pushing down on a diaphragm which restricts the fuel leaving the rail. Unlike a standard FPR, there is an adjuster screw on top which you adjust to change how much force is on the spring/diaphragm. This sets the base fuel pressure. This is the basics of an adjustable fuel pressure regulator.

In the case of a factory FPR, a vacuum line is hooked up to the upper chamber. When throttle is applied and vacuum drops (or it goes into boost), the upper chamber puts pressure on the diaphragm and the fuel pressure goes up. An adjustable FPR will have an additional valve that you set to bleed off pressure so the chamber doesn't see full boost pressure and potentially give too much pressure to the injectors which would then over fuel the A/F mixture.

Basically, you're fiddling with the base pressure and boost bleed valve to increase fuel pressure (and injector flow) past what the limited ecu already does. In the case of my Corrado, it was used because the original turbo chip was able to adjust timing, but the MAF was maxing out how much air it could read. It used the boost pressure to gauge how much extra air was going into the engine.. like a mechanical version of what a modern computer does with a MAP sensor.

But now, with advanced ecu tuners and factory turbo cars everywhere, few people need these. And that's why I have an unsellable chunk of machined billet aluminum FPR that I bought for ~$450.

[mushroom_curry]

Damn. That's intriguing... Didn't realize there was so much of this info that I wasn't up on in terms of custom turbo setups.

Speaking of aluminum, I want those driverside engine covers you have!

[Dreamstate]

Yeah dude, you didn't answer in our phone messaging. Do you want the upper AND the lower, or just the upper?

[mushroom_curry]

Both yo.

You msgd on google hangouts and I don't even know how to get back to the msg without digging for the notification.

It's a ghost messaging system to moi.

[Dreamstate]

No worries. I'll put the package together tonight.

[mushroom_curry]

I think the turbo question comes down to MAF sensors and whether or not the setup incorporates a wideband O2 sensor.

Early 1.8t stuff (AEB drive by cable) doesnt have wideband capabilities, so you are much more rigid when it comes to tunes.

However, turbos that flow similarly can be swapped for one another.