Tuning Tips And Tricks - Turbo Buick Basics, Part 8
Tuning tips and tricks towards better drivability, less turbo lag, and lower e.t.'s.
From the March, 2012 issue of GM High-Tech Performance
By Dan Foley
Photography by The Author
In the last episode (September, 2011) we promised we'd take our buddy Tim Cairone's '87 Buick GN back to Atco Dragway to strip-test its latest combination. Well, we made it back to Atco, but we went ill prepared and were nonetheless disappointed. (Note: never take a Turbo Buick to the track without knowing your car can't even do a 5-psi powerbrake burnout.) Quickly, we learned the importance of proper tuning and preparation before running a Turbo Buick at the strip. Unbeknown to us, the timing (ignition and injector pulse) was way off, causing terrible turbo lag. At the starting line while power-braking for our holeshot, we couldn't even build more than 3-psi of boost. Full boost (20-21psi) didn't develop until we were over 100-feet downtrack causing the GN to run disappointingly low to mid 12's (we were expecting to go mid 11's). We later found out the timing issue was because we didn't install the cam positioning sensor properly (it was 180-degrees out) when we swapped to the forged short-block in Part 7. Then, during a test ride, after setting the Cam Positioning Sensor (CPS) timing, another EGR leak (there was also an EGR leak in Part 7) came back to haunt us. This time the EGR block-off plate we installed blew-out its gasket causing a vacuum leak and turbo lag.
First for this installment we'll show the importance of having the right tool to properly set the timing of the CPS. Second, we'll attend to the EGR issue. Third, we ordered a new chip from Turbo Tweak for our latest combination (ported heads, roller cam, larger turbo, and intercooler neck). Fourth, we'll port/polish and blend the wastegate hole in the new 62mm Precision Turbo for quicker spool-up. Then it's back to Tune Time Performance to dial in all the upgrades we featured in part 6 and 7.
Our first tuning concern was to set the timing of the Cam Positioning Sensor (CPS) with the special tool we ordered from Caspers Electronics. The CPS actually controls the injector pulse timing. Once the timing of the CPS was set properly, a test drive confirmed better throttle response and turbo spool up. After our enthusiastic test drive, we noticed the EGR gasket was leaking. For the fix we pulled the EGR plate off and installed a new EGR valve and gasket. Once again the Buick was running better, but we were not done yet!
Next we installed the new custom chip from Turbo Tweak. We ordered it for a 50/50 race gas/pump gas mix. TT burned us a chip for our latest combo (62 mm turbo, ported heads, roller cam, larger intercooler neck) with additional timing and fuel mixture for using 100 to 105 octane fuel. This new chip will increase the ignition timing from the old chip's 19/17-degrees to 23/20-degrees at full boost. Also the old chip was set-up for 15-17psi while the new one is 20-22psi boost. Since it's programmable, we'll be able to add or reduce timing and change the fuel mixture (richer/leaner) for a safe air/fuel mixture. In the meantime, we'll keep a close eye on the A/F gauge. After swapping chips, a test-drive revealed a smoother, more responsive running engine, quicker spool-up along with a now perfect A/F (14.7 to 15.1) at idle. With the old chip the A/F at WOT (according to the GN's A/F gauge) was a risky 12.1 to 12.4 at 20-21 psi boost. Now we observed a safe A/F in the mid-10's at full boost and WOT. On the dyno we'll tune the full boost A/F to be in the safe zone of 11.5 to 11.9:1. Big kudos to Turbo Tweak after considering we still have only 42 lb injectors, up to this point the GN has never ran stronger!
The final mod, for icing on the cake, was to port the wastegate hole of the turbo. Both our friends at Precision Turbo and Jose Motorsports recommended we perform this modification. This mod is said to help quicken turbo spool up and help hold consistent/steady boost output. The port work needs to be done very carefully while not exceeding a 1/8-inch from the impression circle made from the wastegate puck (see captions 7 and 8). A test ride revealed that we ported the wastegate hole a hair too much bringing us once again back to terrible turbo lag. Thank goodness RJC Racing came to our rescue. They offer a larger diameter wastegate puck (1.65-inch diameter, stock is 1.1-inch) to solve our turbo-lag dilemmaùthis must have happened to other over-enthusiastic folks when they enlarged the wastegate hole!
Once the larger RJC Racing wastegate puck was installed, the Buick was back to running great! According to Tim it ran so strong, he adjusted the RJC Racing boost control valve, so there was only 18-psi boost (20-21psi previously). Note: both Precision Turbo and Turbo Tweak mentioned we could safely run up to 22-psi with a 50/50 race/pump gas mix. With 24-26 psi, 110-plus octane race gas is necessary. With a more miles on the fresh motor, and a few more tweaks we'll be ready to turn it up. For now we were happy to be running strong and ready to go back to the dyno for a safe and conservative tune.
An appointment was made at our favorite local dyno tuning shop, Tune Time Performance in Toms River, New Jersey. Matt Hauffe has been handling driving and tuning duties to the Turbo Regal right from the beginning of Turbo Buick Basics. On our first pass we were pleased to learn the A/F was at a near perfect 11.5 (according to the wideband O2 sensor on their Mustang dynamometer). The A/F gauge readings on the GN were off a point (10.5 A/F) due to a buildup of tetraethyl lead from the leaded race fuel we mix with 93-octane unleaded pump gas (future use of unleaded race gas or meth injection is needed). Spinning the dyno wheels we observed the turbo V-6 was making 30 lb-ft more torque with close to the same horsepower. That's impressive considering there is 2-3 psi less boost (18 psi now, 20-21 psi before)! That only showed us the importance of the right size turbo along with proper tuning. Also, Turbo Tweak knows its business when it comes to burning a PROM chip for anyone with a Turbo Regal.
1 Here’s a must-have tool...
1 Here’s a must-have tool every Turbo Buick owner needs in their toolbox. Caspers Electronics offers this Cam Positioning Sensor tool (PN 102075) to properly set the cam sensor. The Cam Positioning Sensor (CPS) is responsible for the injector pulse timing. We should have used this important tool in the last installment before firing-up the engine, doing any dyno-tuning or going to the track. Our results and drivability would have been much better too!
With a couple of baseline pulls established, Matt added 2-degrees of timing, so there would be a total of 22-degrees at WOT and full boost. Also about 10-percent less fuel was programmed into the tune. On the next spin Matt's fine tuning added 9 lb-ft torque and 5-rwhp (554 lb-ft, 365-rwhp) showing an ideal A/F of 11.7. With straight race gas or meth injection we could have safely used 25 to 26-degrees timing or cranked the boost up to 25-26psi (best efficiency range for our 62mm Precision Turbo is 20 to 28 psi). In a future feature of "Turbo Buick Basics," we'll see how much more power the little V-6 can safely handle. For now and in the next episode, we'll strip test this little torque monster in its safe street tune.
2 We found the cam positioning...
2 We found the cam positioning sensor assembly, which replaced the Buick V-6 ignition distributor, was 180-degrees out of timing. To get started, the timing groove on the harmonic balancer needs to be lined up to the “0” mark in the timing window. Just follow the detailed instructions and illustrations provided with the tool which will light up when the CPS is set properly at 25-degrees.
3a The leaky EGR valve from...
3a The leaky EGR valve from Part 7 was replaced with this aluminum block-off plate.
3b It blew-out its gasket...
3b It blew-out its gasket during an aggressive test drive while we monitored the boost and A/F gauges.
3c Since the stock hold down...
3c Since the stock hold down is designed to clamp down more area on a stock EGR valve, we used a stock-type replacement EGR valve for a better gasket seal with less chance of gasket failure. Without the leak the GN was on its way to becoming a strong runner!
4a A chip change was long...
4a A chip change was long overdue. The chip to the right was employed since the engine and turbo were bone stock...
4b Turbo Tweak burnt us a...
4b Turbo Tweak burnt us a new chip (left) for our latest combo (larger turbo, ported heads, roller cam, hi-flow exhaust, converter stall, etc.) burning a 50/50 mix of pump/race gas (93/110 octane, roughly 100 to 105 octane). Our test drive confirmed much quicker acceleration, spool-up, and a 2-psi increase in boost.
5 This is a reminder shot...
5 This is a reminder shot as to how easy and where the chip location (passenger kick panel) is. A chip change is extremely important when making any changes to a TB. For anyone with a bone stock or breathed-on Turbo Buick, it’ll easily add lots of performance—safely. When ordering a new chip, be sure to completely fill out the spec sheet so Turbo Tweak can burn you a chip which will safely boost performance.
6 Look at the idle A/F (14.7...
6 Look at the idle A/F (14.7 to 15.0 is usually considered perfect) after we installed the new chip. Our test drive confirmed quicker acceleration, turbo spool-up and a 2-psi increase in boost. The A/F at WOT and full boost was safe yet a little rich, at 10.1 to 10.5. Since the Turbo Tweak chip is programmable, we’ll shoot for an A/F of 11.5 to 11.9 when we go to dyno test and tune.
7 Tim’s Buick was running...
7 Tim’s Buick was running better than ever, so we were reluctant to remove the turbo to enlarge the wastegate hole. But both Precision Turbo and Jose Motosports recommend this mod to aid quicker spool-up, so we did it. The wastegate puck will leave an impression where it seals up on the turbine housing of the turbo.
8a We used a die grinder...
8a We used a die grinder with a carbide bit and sanding rolls to enlarge the hole to within an 1/8-inch of the impression.
8b ...As you can see, we...
8b ...As you can see, we tried to do a nice job. Notice that we rolled the edges on the inside of the turbo housing. We remounted the turbo and downpipe to go for a test ride and became quickly disappointed. Terrible turbo lag was back and we lost over 5-psi boost. Apparently we enlarged the hole just a hair too much.
9 Here’s the wastegate puck...
9 Here’s the wastegate puck that needs to be perfectly sealed over the entire wastegate hole during spool-up. If there’s not enough sealing surface (not a thin lip edge like us) for the puck to seal, it’ll cause a small leak and very slow spool-up (our situation). That small leak was causing the exhaust energy to be diverted away from the turbine wheel—enough for us to experience terrible turbo lag.
|Stock, 13 psi
||208 @ 4000
||256 @ 3000
|Chip, 17 psi
||210 @ 4000
||320 @ 3000
|Valvesprings, fuel pump, hotwire
||238 @ 4100
||358 @ 3000
|42-lb Injectors, chip, 19psi
||240 @ 4000
||405 @ 3000
||276 @ 4000
||440 @ 3000
|58mm turbo, 20psi
||303 @ 4500
||440 @ 3500
|104.68 3-in. pownpipe, bost controller
||303 @ 4500
||450 @ 3000
|ADPP, ported throttle body
||303 @ 4500
||446 @ 3000
|Rebuilt trans, 2800 stall converter
||289 @ 4500
||465 @ 3100
|Roller cam, ported heads, headers, 17psi
||339 @ 4000
||465 @ 3800
|62 turbo, hi-flow intercooler ends, 20psi
||372 @ 4800
||515 @ 3500
|Chip, port turbo, w/g puck, tune, 18psi
||365 @ 4700
||554 @ 3400
||(Look for 11's next time!)
10 We were fortunate that...
10 We were fortunate that RJC Racing offers this larger diameter (1.65-inch) wastegate puck. This bigger puck will definitely seal up the wastegate hole we enlarged too much. Now the exhaust energy will be able to more quickly spin the turbine wheel for quicker spool-up and less turbo lag.
11 To remove the wastegate...
11 To remove the wastegate puck, we grinded off the weld that holds the lever and shaft together.
12 With the stock puck removed...
12 With the stock puck removed you can see the size difference (stock 1.1-inch, RJC Racing 1.65-inch).
13 When we trial fitted,...
13 When we trial fitted, the new larger puck was hitting the inside edge of the downpipe flange. Here we are making a sizing adjustment, so the puck would have roughly an 1/8-inch of clearance once it’s installed. Check out caption #9 for the amount of clearance there was with the smaller puck.
14 Also the lever was hitting...
14 Also the lever was hitting the outside of the flange, so we did some more clearance grinding. Good thing the downpipe has a thick flange!
15 Here final sizing shows...
15 Here final sizing shows enough clearance for the lever and the puck. Notice the puck and the lever are even and level to each other.
16 The lever and the shaft...
16 The lever and the shaft were joined and held together with a little weld. Be sure the shaft and lever has enough side-play (.020 to .050-inch) for proper wastegate operation.
17 Here’s the latest look...
17 Here’s the latest look at “Turbo Buick Basics.” Right from the beginning we only wanted to update it to become a better street driver with competitive performance that’s equal to or better than the average late-model performance car.
18 On the baseline pull after...
18 On the baseline pull after applying the aforementioned tuning basics and with only 18-psi boost, we were pleased to learn torque was up to 545 lb-ft, for a 30 lb-ft increase! Power was close to the same at 362-rwhp and the A/F was a safe 11.5:1. Since the motor is still somewhat fresh (800-miles), we decided to add only 2-degrees timing and go 10-percent leaner on the fuel enrichment. This brought the chilled-air machine’s torque upward to 554 lb-ft and 365-rwhp with an ideal 11.7:1 A/F. At that we called it a day. Next stop will be the track before we start turning up the boost.