lol, stomp on it at 4k rpm in 3rd and Xanax may be needed.

Irishace, the internals are stock. All of the hoses/gaskets etc were replaced but the internals untouched.

I figured the Xona XR980 I purchased (based on the 3073 I believe) would be a good compromise between the 3071 and 3076. The 3076 may ultimately have more topend power but not quite as responsive, and presumably the 3071 is a bit more responsive but not as much topend.

I'm on v3 of the tune and in 4th gear with the sunroof up and 88 degrees outside and full tank of gas I did a 75-110mph pull in 3.7s which is the best I ever saw with the Champion 68s on a much cooler day with less than a full tank of gas

 

I believe it...I haven't even tweaked the boost curve yet. I know I asked you this in an email, but I think your response got autocorrected a little, lol: since the manifold pressure reading via the hks is a little bit higher than the car's map sensor reading pre-throttle should I be lowering my target or is it "ok" to see high 23ish psi in the manifold (while the pre-throttle reading is around 22.5psi)? This is above 4.5k rpm that I'm talking about.

 

lol. I was actually thinking that the stock map sensor may be maxed out.

 

It's been a while since I drove the car with 68s but I thought the turbo tip-in was ok. What I noticed with both the 68s and the Xonas is that when datalogging if you start at 3k rpm and just stomp it then it seems to ever so slightly bog. But if you squeeze the throttle a little and then stomp on it it takes off better. This doesn't happen in "real world" driving because usually in 3rd or 4th gear if I was going to stomp on it then I'd be above 3500rpm. In that scenario I find the Xona tip-in to be just as good as the 68s were but memory is fickle. I don't know how accurate the "calculated load" is in the Cobb datalog but if it is accurate then the 68s have more load below 4200rpm but at 4200rpm they are the same and then the Xona have more load above 4200rpm.

Subjectively, the Xonas really pull even in 90degree heat like today.

I didn't want to give up the things I liked about the vtgs (big torque hump around 4k rpm!) and it looks like you don't have to give up much with the move to Xonas. Obviously you'd get the most from them by building the engine but that wasn't part of my plan. If I hadn't dropped my engine for the coolant pipes I would have just gotten a new Cobb tune for my 68s. The Xona tune is waaay smoother at idle, and the part-throttle transitions are also way better. I think that's where my previous custom tune wasn't as good as it could have been.

 

Are we really talking that 1000 whp can be had on this kit with fuel built motor..that is a crazy number ..for a turbo that can spool like that..
Sorry to thread jack ..Sam do you have specs on thse turbos and if I was looking for 800 +/- what turbos do you recommend from your xona line up...
Keep up the good work bogg

 

I didn't know that.

I am on v3 of the tune. Today was a little cooler at 71F and I did a 60-100 in 3rd gear in 3.0s. I was able to do 3.0-3.1s consistently with the 68s, but I was on revision v19, lol. Did a 75-110mph pull (starting at 74mph and flooring it) in 3.6s which beats my best of 3.7s with the 68s. And there's lots left to tweak in my tune. For example, it's a little rich according to the logs and still fairly conservative with boost at lower rpms.

I just reread PTF's excellent documentary thread on his a3076 build on stock motor. I believe my Xonas are very comparable to his previous generation turbos - something like 56lbs/min vs 57 so I was interested in his pumpgas results with the same gas I use. He was able to get the 60-100 down to 2.7 or 2.8 on pumpgas alone on 20ish psi boost max. That's pretty much what I'm aiming for. Right now my max boost is 22.5 pre-throttle body (which is probably higher since the boost sensor is maxed) and hits 24psi on the hks which reads the actual manifold pressure. I'm hoping with the fine tuning that I will lower the peak boost pressure. But then again, if it's not necessary I won't worry about it. He was making 20psi at high 3k rpm which is much more than I am currently making...

2nd gear has always been a rush but when I floored it in 2nd today it was profoundly awesome. There's just a certain sense of ease with these turbos compared to my 68s, and I believe a portion of that is tune related.

I'll get the pics and build log going as soon as I get a chance...

 

You're right, there's a trick to 60-130s etc..., but that's why I came up with my own way of comparing real world performance for an idea of how a car would perform in a roll race scenario with my 75-110 metric. Anyone can plant a foot on the accelerator at 74mph in 4th gear and the performance doesn't depend on any driver skill, just the capability of the car...

 

Seems like your having a great time ..any chance posting a video

 

Great thread! Glad you are enjoying the car with new found power!

-Mitch

 

If you're talking about one of those self-incriminating videos where I film myself thrashing the car then I'm afraid not.

I don't have a gopro and hanging onto the cellphone while hitting it in 3rd gear isn't wise. Pretty much need both hands on the wheel.

I have build pics which I'll post as soon as I sort them.

 

Thanks Mitch! The accessport is the best thing since sliced bread.

 

It's not a matter of the turbo being used (between these two), but how hard you push it. I actually run 2.56s in 4th gear 75-110 mph on VTGs like your 68s.

Your Xonas should do better or equal technically but you have to keep torque down on a non built engine or it will blow. Don't let you get exited on chasing times. The car can be much quicker, but it also can break more easily.

On my car (996) I run Tial A2871 and these can push really hard and produce 800 to the wheels with a little headroom left. 3073 should be a perfect fit, especially on higher revs because of the lack of backpressure compared to VTG.

 

Jeez no ..this is not YouTube ...more like a dyno and when does boost kick in vid...

 

if you go PSI for PSI on Xona 30xx vs Any VTG Hybrid. Holding all else constant the Xonas will make more HP at every boost level every time. They also drive smoother than the VTGs.


With that said you ARE right and Xonas are meant to live above 1.5 bar and some larger ones above 2.0 bar, that's where they really shine.

 

I'm seeing 1.5-1.6bar in the 4400-5400rpm band currently. We are still fine tuning the AFRs and load targets so I haven't done any adjustments with the boost controller apart from setting a 20psi target. There is obviously some overshoot but we'll deal with that soon enough....

The Xonas do feel smoother than the 68s did overall. My goals for the Xonas are relatively modest - not looking to break any records, or rods. Just hoping for some modest improvement in the standard performance metrics. If I could knock off half sec or more from my 6.9s 60-130 on the 68s on the same pumpgas I'd be happy.