So it was a mixed weekend for me this time out. Once again the car ran good the first day and the racing Gods struck me down the second day...

After showing up to the track friday morning to go through some NASA instructor training (if you can imagine me being an instructor ) and putting in a new clutch the week before I felt good about where the car was. I know I still need some more tuning time and some suspension tweaks but overall the car feels good. I slapped on the RA-1's and did some last minute checks before going out on course. The temporary harness bar I had a local shop weld in held the harnesses in place tight and I strapped myself in.

The track was fun as usual. The first session of the day was more of a warm up for me and the car. Everything felt pretty good. The car is damn fast, even on 17 lbs of boost (wastegate spring pressure). I was able to come out of turns at very fast speeds. I started noticing early-on however, that the BOV was still not allowing me to go through long sweepers at part boost. It kept releasing air and making the car shudder - not too much fun when you're doing 75 mph around a sweeping right hander and you have to let off and unsettle the car. So I eased up on it a little at the expense of slower lap times. Oh well.

Knowing that I wasn't going to put down my best times I decided to just have fun and go fast in other areas of the track. And boy was it fun! The brakes were doing awesome, the water temps were staying in check, the tires were gripping well, and the oil temps were still climbing due to the dump tube being right next to the oil filter - so I would take it easy for a few laps every so often.

The afternoon wound down and I was getting ready for the night enduro that we were going to be doing. With few cars out on the track my friend and I went out and got about an hour of track time in the dark. Damn what a rush! It's pretty scary when you can't see your reference points but it's a blast. Coming up over the crest in turn 6 and you have flood lights from the front straight blinding you... oh yeah. At the end of the day I was the third fastest of all the TT/HPDE 4 guys. About 3/4 of a second back on the second place guy and 2 seconds off the 1st place guy. I'm confident I can shave off a good amount of time off my lap times at that track once I get the bugs worked out. I shut the car off and called it a night with no issues the first day. I think my best time of the day was a 1:48 - not great really, but still 2ned or 3rd fastest of all the TT/HPDE 4 cars out there. The first place guy out there was running consistent 1:46's, and I know I could have beat that if all was working well with the car.

Day two:

Did a few checks on the car and headed out for the first run. I brought one of the instructors along as he wanted a ride. I get through the first warm up lap and start heading out on the main straight - I let of the gas and it keeps going. I hit about 130mph with the throttle stuck open. Push the clutch in and the engine revs to 8k then falls back down. Damn it! Not again. I take a few more turns and it does the same thing... have to bring it in to see if I can figure this damn thing out. The instructor was a bit disappointed, as he wanted to see how the car handled with all of the speed it had (and I wanted to show him!).

I park the car and pop the hood. But before I could even look at the throttle cable I see coolant spewing out onto my lower intercooler pipe. WTF Looking at it a little closer it appears that the wastegate banjo bolt worked it's way out and fell off, wedging itself in between the I/C pipe and the radiator - guess which surface lost that battle. I pry the bolt out and try to assess the damage. The head of the bolt was rubbing perfectly on one of the fins causing a crack. Looks like my day is done before it even got started.

I let the remaining coolant drain out and clean the hole up to get a better look. Since I drove the car down to the track (1.5 hours away) I am now thinking in terms of how to get the car home. My buddy hands me the JB Weld and I get to work.

After letting it cure for a few hours I fill it up with water and can see no leaks. Luckily I was able to drive it home with no issues. Unfortunately my buddy's car had an alternator die on him late Sunday evening when all the parts stores were closed. He had to make arrangements with some of the other NASA guys for a tow. All in all it was a fun weekend but yet again the car was parked on the 2nd day of a two day event.

I'm wondering now if I should just assume the JB Weld is a permanent fix or start making other plans. I'm going to ditch the infamous banjo bolt for something else on the wastegate, change the spring in the BOV for better low boost driveability, and try and figure out why the hell the throttle keeps sticking. All minor fixes but important ones. The car should be ready for Hastings, the next NASA event on the schedule (6 hours away from me).

In regards to the part throttle compressor surge, the BOV spring may not help entirely(but it will help the car blow off from low boost levels when letting off the gas). Part throttle surge is just a fact of life for larger turbos on smaller engines. The turbo is spooling too quickly while the engine is flow limited by the throttle, so you end up on the left side of the surge line on the compressor wheel map.

Three things that come to mind to solve this are:

1) Switch to a larger exhaust turbine and/or housing, which could slow spool enough to keep the problem from happening. The downside is of course a later spool RPM and reduced transient boost response while gaining some more top end power.

2) Switch to a smaller compressor wheel less prone to surge, giving you slightly better spool at the expense of top end power.

3) Run a really light spring in the BOV such that it vents air and allows the turbo to flow enough air to stay out of the surge area, i.e. an intentional boost leak. I'm not sure if the '7psi spring' will be light enough, but it could be. You'd have to measure the air pressure before and after the throttlebody to get a ballpark figure on what you need. On a wild guess I'd say you're looking more at a 4psi spring. The downside to this option is that the BOV will be open at idle with that weak of a spring.

His first day out was a lot of fun. The first one we saw, his car was FAST coming back to start finish, but the bad part of PMI is you cannot see the whole road course due to the dips and trees in the middle. You really seemed to have a blast everytime we saw you come back in. Sorry to hear day 2 went as it did. As an instructor, from just what I saw, You are very patient and know what you are doing. I was impress. . We are working on making it to Nebraska with the Talon finally. Already cleared it with My boss.
Mike

wortdog said:

In regards to the part throttle compressor surge, the BOV spring may not help entirely(but it will help the car blow off from low boost levels when letting off the gas). Part throttle surge is just a fact of life for larger turbos on smaller engines. The turbo is spooling too quickly while the engine is flow limited by the throttle, so you end up on the left side of the surge line on the compressor wheel map.

Three things that come to mind to solve this are:

1) Switch to a larger exhaust turbine and/or housing, which could slow spool enough to keep the problem from happening. The downside is of course a later spool RPM and reduced transient boost response while gaining some more top end power.

2) Switch to a smaller compressor wheel less prone to surge, giving you slightly better spool at the expense of top end power.

3) Run a really light spring in the BOV such that it vents air and allows the turbo to flow enough air to stay out of the surge area, i.e. an intentional boost leak. I'm not sure if the '7psi spring' will be light enough, but it could be. You'd have to measure the air pressure before and after the throttlebody to get a ballpark figure on what you need. On a wild guess I'd say you're looking more at a 4psi spring. The downside to this option is that the BOV will be open at idle with that weak of a spring.

Click to expand...

Well since I can't really do 1 or 2, I'll have to try 3.

Ludachris said:

Well since I can't really do 1 or 2, I'll have to try 3.

Click to expand...

What is it with wastegates? The internal set screws in mine vibrated out, so I had to run Autobahn at 15 psi -- 8 psi off the normal 23 psi.

Can't wait to get on the same track with you at Hastings. What class are you? I will register in TTS (dynoed 355 hp) once I solve my log-in issues with NASA.

Rich

Slow old poop said:

What is it with wastegates? The internal set screws in mine vibrated out, so I had to run Autobahn at 15 psi -- 8 psi off the normal 23 psi.

Can't wait to get on the same track with you at Hastings. What class are you? I will register in TTS (dynoed 355 hp) once I solve my log-in issues with NASA.

Rich

Click to expand...

The hats are aluminum and when it heats up the metal expands. You might want to try tightening all of your bolts after heating up the wastegate. If you ever want to take off the hat or the banjo bolt, you will probably want to heat it up to do so.