SRadke said:
Spoolup speed is determined by how much fuel you hit them with. Most of the guys with 66's push a lot of fuel. The smaller turbos with lighter compressors and turbines will spool faster when hit with the same amout of fuel, less rotational mass. There are small exceptions to this in design and ball bearing tubo's are diffrent altogether but we'll try to keep this on point.
If you're running a TST with the stock turbo you'll have safe temps (less than 1250°) through about setting 3:3... . maybe into setting 4:4. If you go with a 62mm compressor like the HTB2 you'll gain up to 5:5. Step up to the 66's and you can have 6:6. The advanteages to any of the aftermarket models mentioned here is that they're tough. The'll take a good shot of abuse and keep on spinning.
All of these units will have a wastegate built in and come factory set for something around 40 psi. If you're looking for a good reliable driver leave it there.
As for the "Super B" throw it in the class with the other 62mm turbo's.
-Scott
Listen to Scott - lots of info in the above quote! Before I got my SPS66 I ran first an HTB2 w/62 mm compressor and 12 cm2 exhaust. This spooled super quick when I ran a TST, but I was majorly limited on the upper end in terms of EGT and drive pressure. With the TST it would just blow right by the 40 psi wastegate setting to about 45 psi in a blink of an eye. I was constantly watching gauges and wondering WHEN not IF the turbo would pop. Fortunately, it never did, which is a testament to its tough design, but it was a nerve wracking way to drive always having to watch gauges. Maximum TST levels where I felt my comfort level start severely dropping off were as Scott indicated above for a 62 mm compressor.
I then got rid of the TST due to my truck having unresolved driveability "issues" with it and exchanged the exhaust housing for a 14 cm2 to handle 100 HP injectors plus simple pressure box. This turbo had reasonable cooling ability until I got to the mid-to-upper box settings. Boost rise rate was a noticeably slower and lower too, which gave peace of mind when driving. Only when the pressure box was turned to 100% did the down low fueling come even close to a TST on any mid-range Te setting.
Then last month I had an opportunity to drive a buddies truck with a SP66 with a pressure box stacked with TST and 35" tires. With just the pressure box on 50% and TST on low settings or off his truck responded and drove great - even with 3. 73 gears and 35" tires! I was impressed and sold on the SP66 and then eventually got the SPS66 due to circumstances falling into place at the right time and place when I had injector problems and had the Industrial Injection guys diagnose them
. My buddy uses his truck to tow regularily when not sled pulling or racing ricers and has had 0/zip/nada towing issues. Before he got the SP66, he blew up 2-3 stock turbos, an early ATS turbo in minutes after the 300-mile break-in, had a Killer B2 (HTB2 64/14) with major surging, and then eventually upgraded it to his present SP66 after HTT worked with him quite a bit to test different designs between the Killer B2 and SP66.
I'm not saying there isn't any surging with my 66. Heck I still don't know what to look for! So if I have experienced it, I probably unknowingly programmed myself to drive through it!
The only thing I have noticed with mine when towing is SOMETIMES at 2100 rpms or so in 5th or 6th at steady pedal pressure the rpms and boost and then speed will drop and then pick up again to the initial speed. I am kind of wondering though if this is the Juice since the 305/555 version adds fuel pressure until 2100 rpm and maybe it switched to a different map at this point. It NEVER does this when the cruise is on, though - probably because the APPS is not used during cruise. Without cruise on I can make this happen at will pretty much, but at the same time I can power through it to avoid it altogether. So is this surging?? Enquiring minds need to know!
Anyhow, realistically my intended truck usage sounds just like yours. Did I NEED an SPS66? Probably not since the HTB2 62/14 was more than enough for my needs 90% of the time since I don't sled pull or drag race. However, in my case, I just WANTED something for the remaining 10% of the time just in case!
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