OK, I've been reading threads here and there about people who have had the STS kit installed, and from what I can gather, most are saying that their boost kicks in around 3K rpm. Well, here's my dyno chart:



This is with 6 psi of boost, according to the installer.

It appears to me that the boost on my car isn't really kicking in until closer to 4K rpm? So what't the scoop? Is this something that is adjustable somehow? Or are my LGM Pro LT headers really making that much difference on the boost threshhold?

As a comparison, here's the charts right off of STS's website, with only 5 pounds of boost:




So what is going on here?

 

I believe the STS charts were produced at 6 lbs. of boost (at least thats what it says on the STS web site).

What makes you say boost isn't kicking in until 4k? Your TQ and HP climbs linearly from 3.5k up to 4.5k. I would say you are already at full boost (6 lbs) at 3.5k.

 

Assuming the blue line in the upper charts is stock, you're passing the stock numbers at 3500 rpm, which would suggest that it's where you start making boost.
Still not as good as the 2800 in the STS charts though.

 

Looks to me where the dyno operator started the run (3300rpm's) is why its not showing the power coming on earlier

 

That's not what I see on their site -> http://www.ststurbo.com/c5_dyno


C5 Corvette Twin Turbo-

Performance Results ('04 Z06)

Boost: 5 psi Intercooled
Rear Wheel Horsepower: 535
%'d increase: 55%

Rear Wheel Torque: 502
%'d increase: 47%



Well you got me there..... I guess I'll have to look at the gauge and see where the needle is at 3.5K. I have to admit I'm not an expert on these things, but I don't THINK that the boost is at 6 psi at that point at all. Maybe I need to see if HPtuners can capture manifold vacuum/pressure readings and I'll log a few runs to see what it looks like.....

 

Interesting... this link from their data sheet says 6 lbs.
Data Sheet

You may see boost come on later in the lower gears (less load placed on the engine). You might want to try a WOT run in 3rd to put more load on the engine. Also, the engine will rev slower, which will allow you to watch the boost gauge without worrying about engine RPM. Your dyno run was probably done in 4th.

Assuming you have the stock MAP sensor, you won't be able to log boost.

 

Also you will probably see boost quicker on the street than on the dyno unless the dyno operator loads the engine by using the dyno brake before he starts his run...

 

I found this to be true as well.

However, if you follow STS's dyno procedure, your boost will come on earlier as well.

Jim

 

What's the dyno procedure? The lag seems horrible on those dyno sheets. Peak torque at roughly 5000 rpm? I think more focus should be on when you make full boost not when you START to make boost. If you want a linear boost/power increase you can get a centrifugal supercharger, benefit of a turbo is tq at lower rpm not when you are about to shift.

 

your dyno is dropping teh gas at 3400 and sts's dyno is dropping at 2700 or so.....kinda throws things off a lil bit.

 

The boost will come on faster in the real world with full load and heat, but it will atually come on slower in the lower gears (if you have a stick). You will notice that it is really laggy in first and 2nd, but you will probably have traction problems in those gears anyway.

Still fun, but you will never get a remote mount to hit like a front mount setup.

 

i honestly think the wider pipes are causing slower exhaust flow and creating some lag, now if you had bigger cubes to back up the larger diameter, you would hit harder with the turbos, like Cajun's 402 setup but thats just my .02

you are a few steps ahgead of me i havent had mine on a dyno yet

 

Something to the effect of...
Make sure the car is heated to operating temp.
Remove tail lights to help airflow.
Use brake to load car to a certain RPM.

This is to help create street conditions. My tuner didn't do the above, and my boost comes on sooner than what is showing on my dynot sheet.

Rich Z's velocity may also suffering from the headers, taking it longer.

Jiim

 

Boost on my car starts to kick it about 3,200 rpm, but it also depens on what gear I am in. If I am in first gear, it takes almost to 4,000. If I am in fourth geart it kicks in sooner. The turbos need something to build pressure against. On my Porsche, the boost kicks in almost exactly the same rpm, but it spools slightly faster. I think this is due to the shorter distance in tubing.

 

Just to clarify, as engine load is increased/decreased, all turbo systems, regardless of their configuration (e.g., front mount, rear mount, top mount) will experience some shift in where the turbos begin to spool and where max boost is achieved. Of course, the degree of that shift will vary between systems.

 

Gears will help you spool a bit faster.A 402 or 427 has lots of low end grunt you feel no lag and I very often at our shop (XTREME Motorsports)swap out to ceramic ball bearings which spool faster as well.
I have the opposite problem on my C5R I run Garrett T 28's and I'm spooling at 18-2000 rpm and at 7 Lbs. of boost I lay down 900 Lb. Ft of grunty Tqe. so I travel sideways much to often.I'm stepping down from 3:42's to a built 3:15 and doing a hybrid and building the impeller to a T34 hybrid.I will see if these mods and pulling some timing let me spool at 2800-3000 rpm I would be 1 happy camper.At 790 rwhp and 900+ Tqe.(7psi 91 octane base boost) at rpm way to low car has a 1/4 mile best of 11.2 at 140 mph trap speed and thats on BFG drag radials.
Its built for tracking and I will further mod it for superb handling,I would like it to compare with my 575M,maybe a dream but dreams are free,even though the 5500 in suspension isnt.
Good luck to you on your TT set up,if you need any help give us a call.
Dave XTREME 480-517-4969,right now where slammed with a bunch of C6;s and Zo6's but If I can get a tech to make suggestions I will.I would wait 7-10 days were short handed (down 2 techs due to illness) but we should be back on schedule by then.
I know what it feels like to spend 15k+ and want my car asap as promised,this is the 1st time in years that we've been behind schedule but biz is great thank G-D.Dave

 

on my stock A4 with GT 32s and no cats full boost doest hit until closer to 4k unless you spool it. No where near 3k.

 

How much boost are you running?
Jim

 

Do other turbo systems give out specific "dyno instructions"? If you are tuning to get the afr and timing down, do these instructions help?

 

I don't think so, but I have no experience with any other kit.

My tuner would know, not me.

Jim