Originally Posted by Jeff64
I'm hoping you can tell me a little about your Renn tech ECU tune. I'm considering having it done to mine soon, just would like to know your opinion and experience so far, not looking for economy, looking for more pulling power. Also I've ordered the Koni's and spring assist kit from Sprinter store. What's your experience been with them so far? Imprvoved ride or only handling?
I can't tell you exactly how much of an increase in horsepower and torque I actually realized by having the ECU tune done. I haven't done a timed 0-60 before-and-after or anything like that. But I do know that I have better acceleration, which is more noticeable when I'm towing my toad. You're still limited by lag in the turbo, of course; that doesn't go away.
I haven't driven in mountains, only hills. Since having the ECU tune done, though, I haven't once had to manually downshift to go up a hill. Before the ECU tune, I sometimes had to manually downshift because the Interstate waited too long to do it itself and would start to bog down. I can't say for sure, but I think the ECU tune also changes the shift points on the transmission (computer controlled) so that it spends more time at the top of the torque curve in each gear.
When you have the ECU tune done, if you're not taking it directly to RennTech in Florida, your Sprinter dealer will remove the ECU chip and FedEx it off to RennTech. The process takes 7-10 days because it spends more time in transit than it does having the work done.
As for the Koni shocks, they make the Interstate ride more like a truck, which to me is a good thing. It doesn't bounce as much, and so the bumps are harsher when you do hit a bump. Each bounce dissipates energy from the bump, and if you dissipate that energy in fewer bounces, naturally the ride will feel harsher. I can accept that, because that harsher ride is the price of improved stability.