Quote:
Originally Posted by RarlyL8
Nice that you are looking at VNTs! Will you have the opportunity to directly compare with a conventional turbo by swapping one in place of the VNT? The typical modified CIS 3.3L 930 engine can hit 375whp with 1.0bar all in by 3000rpm, I don't know what that would look like on a 2.7L engine or what a VNT would look like on the 3.3L low C/R 930 engine. I played around with the old school VNTs 20+ years ago (no computer aids or EFI) and while they did improve drivability full boost didn't come any earlier. EFI and computerized engine management alone helps performance and reduces turbo lag which muddies the waters when trying to compare.
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VNT / VGT (Basically the same tech) turbos require careful calibration to realize all the performance. This means AT LEAST a 3D control map, though factory style calibration has a multitude of 4d mapping.
If you look at my dynos, there is a somewhat direct comparison to a EFR 7670 WITH a quick spool valve. I don't know why I forgot to mention that part of the old setup - I'll go back and edit it!
Spool is basically irrelevant on it's own - what matters is the torque band! What's much harder to show / prove is the boost response in important areas.
The VGT turbo in this setup absolutely DESTROYS the response of the EFR 7670 - a turbo that already responds MUCH faster than a "traditional turbo"
Example, from my experience having driving 100s of turbo Porsches:
4000 rpm - decel to full throttle:
Stock style turbo (tuned and bolt-on upgrades etc): About 1-1.5 seconds to full power. Old school turbo tech, but still pretty fun and fast!
Modern ball bearing turbo (EFR 7670 or similar, properly sized performance turbo): About 0.4- 0.6 seconds to full power response. Huge upgrade over an older style unit. Cars feel awesome like this!
VGT turbo: the power comes on as fast as you can put your foot down. There is essentially ZERO perceptible lag. 1/4 second to full power, or less. The engine feels like it's triple is actual displacement, or like a very healthy supercharged setup.
I hope that helps explain just what these things can do! It's not just about the quicker spool and low end gain (though that's a primary benefit!) - the boost response is one of the most noticeable changes. Complete transformation over a normal turbocharger.
I'm not a "keep everything secret" guy. Here's my data for control on the Porsche VGT unit. Please note this could use a bit more work, and will change with different engine and exhaust setups etc:
Please note - running other duty cycle frequencies or duty cycle below 20% or above 80% results in the controller going to to fault mode. The fault will not reset until power has been cycled to the controller. (this was fun to learn)
I still plan on making a stand alone controller for the VGT turbos, for guys with less advanced ECUs or that just don't have the available outputs.