Question: How much boost?

[boostedmaxPSI]

How much boost are my fellow Callaway Twin Turbo owners running? Just gauging to see if most owners are satisfied with the stock setting of 10psi for the stock wonderbar or 12psi for the bigger wonderbar.

I currently have mine tuned to about 12.5psi.

Has anyone ventured beyond 12.5? Has anyone figured out what 1 or 2 extra psi equates to in TQ and HP for our motors?

Does anyone know someone who has experimented with more then 15psi? 632C2 once dumped 22psi and put up some amazing numbers.

 

[*89x2*]

...are you thinking of going for the "black" springs???


I am at 54hg's



BTW, another question to ask, is how many have had boost creep w/o cats???

 

[SurfnSun]

Frank mine was set around 56" hg...i usually had a little bit of boost spike to 58" then it would settle down to 56"

The key is making sure the EGR system is working at 100%. After I switched to the green springs even with the allen screws all the way it I couldn't get more than 50-52"

I believe the red springs will make all the boost you want

 

[calawyclif]

Well it was a long time ago after a tune up at callaway...my car was a monster nothing like i ever felt before...when I called back callaway I actually spoke with Reeves who happened to be there ( back in 1991 or so ) and told him about the power increase and what the drawback was...he told me that I would drastically reduce the life of the motor if I left the boost where it was( unfortunately I dont remember the exact number but 58" comes to mind ) He had also mentioned a hp and torque numbers to me but dont remember at the moment..pretty sure it was about 16-18 hp per inch though.

Maybe somebody else can be more precise with hp and tq numbers...happy new year to all

 

[89onlyZ51]

Still running stock 10psi here. The bigger question is when you increase boost, what are you doing for fueling/engine management? The more I understand the MAF/Microfueler combo that's on my '87, the less I like it. I would not feel comfortable increasing boost without better control over fuel and spark. There is just too much guessing and assumptions with that setup.

Regarding how much HP per lb of boost. There is a rule of thumb that works reasonably well. Take NA HP * {(boost +14.7)/14.7} and that will approximate your boosted HP.

For a stock '87, I assume the naturally-aspirated HP is about 200 due to the 2 pt lower compression ratio. (Another rule of thumb says you lose 10% of you HP for each CR point drop.) So, 200*(10psi+14.7)/14.7 is 336, pretty close to the 345 rating. With 11 psi, it becomes 350 hp - an increase of about 14hp.

 

[boostedmaxPSI]

from the initial responses, it looks like 12psi is the norm. Hope more folks respond.

Calawyclif, that's an interesting statement that Reeves made to you. Would liked to have a better understanding of what he meant by that. Do you have the big wonderbar in your '89?

89onlyZ51, I dumped the microfueler, "MF'r" a long time ago and now run another product that allows easy adjustment of fuel when I tune on the dyno. I have close to 50 dyno pulls for tuning to ensure proper tuning. The MF'r was the reason for most of the pulls. Once I dumped the MF'r my Twin Turbo has been sooooo much better to drive and the power band is much smoother.

89x2, not ready for the black spring I agree with Surfnsun my red springs are more then plenty.

I head back to the dyno this morning to tune in 15psi just for fun to see what the difference in power will be from 12.5psi to 15psi. A/F will be adjusted using my AIC and KR will be monitored. We'll see...

 

[SurfnSun]

Are these the numbers youre shooting for?

 

[boostedmaxPSI]

Are these the numbers youre shooting for?

On a MILD tune J/K

Actually I'm not looking for a specific number, I'm more curious about how the car will behave with a little more boost. Remember I still have cats and mufflers.

You've been beating it in me for a year now :bash to make those numbers the cats must go... Let's see if I can get somewhat close with a bit more boost and fuel.

B

 

[89onlyZ51]

You've been beating it in me for a year now :bash to make those numbers the cats must go... Let's see if I can get somewhat close with a bit more boost and fuel.

You can make it with cats; it's gonna be hard with the factory cats, though.

 

[89onlyZ51]

89onlyZ51, I dumped the microfueler, "MF'r" a long time ago and now run another product that allows easy adjustment of fuel when I tune on the dyno. I have close to 50 dyno pulls for tuning to ensure proper tuning. The MF'r was the reason for most of the pulls. Once I dumped the MF'r my Twin Turbo has been sooooo much better to drive and the power band is much smoother.

I've been reading up on the speed density conversion and switch-over to the later Syclone/Typhoon ECU which can see boost. I may give that a try since it's an easy (and reversible) swap, and others have reported huge gains in driveability and tunability after making the switch.

 

[*89x2*]

...this post won me a case of warm beer

my guess, the closest one to the actual numbers = 333h/488t @ rr wheels

Hi everyone! What's the real world rear wheel performance specs on a "stock" 1987 Callaway Twin Turbo Corvette ? Well, let's find out! I've been very curious myself and now the time has come to find out!

Let's play like this.. everyone post their respective guesses like this:

300 hp / 475 tq
_____________________________________________

Let's say the actual peak numbers from the graph turn out to be 325hp / 525tq. What we'll do then is take your guesses and subtract them from the actuals. In other words for hp 300-325= 25 and tq is 475-525=50. (We're only taking positive integers as a result-- this way it doesn't matter if you guess high or low). From there-- add the two results together (25 + 50 = 75) So, just for numbers sake-- you were 75 points off. Again, the closer you are.. the lower the number of points. The person that guesses the closest obviously gets the least points and you WIN!!

A couple pointers, hints and guidelines for this contest:

1) We are looking for PEAK SAE corrected figures as generated by a Dynojet 248e. Averages are not counted and also realize that the peak numbers for both torque and horsepower occur at different rpm levels. We're not looking for an rpm pointer guess.. merely just the PEAK numbers as shown on the graph.
2) Hint- on the street this car pulls and pulls like a mutha. Neck snapping torque is absolutely phenomenal!!
3) Related to number 2- the car is stock. Yeah, yeah.. the air filter is a K&N and the lid is cut. Everything else on this car is Callaway issue and has been calibrated by their technicians to their specifications. Most updates have been done to '91 specs.
4) The cats are still in place and we aren't talkin *****.
5) Callaway has updated the turbos to the Rotomaster units.
6) No mufflers are on this car. It has the stock Callaway megaphones on it.
7) It runs 54"-55" Hg at wide open throttle in the "dyno" gear. The car does not exhibit boost creep. 93 octane was used for testing.


IF YOU WIN?? Well, you must stop by the Callaway Owner's Group display at Carlisle from August 22-24 to collect your free case of Yuengling Beer. Shipping is not available. Substitute beers can be requested-- but Yuengling is a damn good beer so let's stick to it! Don't drink and drive! Anyone is eligible to win. Tell all your Corvette friends about this!! Tell them about the CAC and Callaway! :cool

 

[boostedmaxPSI]

Car performed well. No boost creep, no detenation/knock retard. Just short of 60Hg I have 66 dyno pulls on this car and it's truely performing at it's best.

 

[calawyclif]

ooops ..sorry.. I do have the big wonderbar and custom offroad exhaust with megaphones from callaway...he did mention also the time of year was a factor since it was late october and getting cooler outside. He definitely mentioned longevity issues if I decided to keep the boost up to 58" or maybe even 60" dont quite remember the number...All i do remember is how strong it pulled..like crazy. Beleive me it was tough turning it back down I was only 21 at the time and wanted the HP

 

[SurfnSun]

You can make it with cats; it's gonna be hard with the factory cats, though.

Boostedmaxpsi will tell you Ive been harping on this for a long time.

If you want to make big power with these cars you have to do it with BIG exhaust...and preferrably no cats.

You can compare my two dyno sheets. These were done with nothing but an exhaust change. In the first run it was factory exhaust with no cats.

You see an nice smooth and steady increase in power.

Now...add 2.75" true dual Power Effects exhaust system and see the difference. I was at 400rwhp almost 1000rpm earlier!

The difference in the two lines with with the Power Effects closed vs open with changed the boost from 12.5-13lbs(~56"hg) down to ~10psi. Plus the loss of flow from the capped exhaust. On a very cool morning, with the capsuls closed I raced a C5Z06 and pulled him so hard to 165mph it wasn't even funny(we're talking bus lengths). The downside was a popped a wastegate gasket due to the back pressure...it was an easy fix but leart me a lesson :gap

The exhaust change COMPLETELY made it a different car...the turbo spool went from slow to explosive and on a cool day the car was just down right violent to drive. Uncorrected numbers were over 455rwhp/600+rwtq

Another thing I learned from talking to boostedmaxpsi is to dyno with the hood down and use the fan pointed up into the intercooler passages. We used to dyno my car with the hood up and ambient temps around the intercoolers were well over 200 degrees. I think that closing my hood and aiming the fan up as opposed to at the radiator would've brought my numbers up a little more.

 

[boostedmaxPSI]

Calcliff, thanks for sharing your story. I bet Mr. Callaway was more implying just what 89onlyZ51 was getting at earlier in his post and that is you simply cannot turn up the boost and ignore the fuel side. I say this because I'm sure Callaway Cars in 1991, as you mentioned, wasn't too keen on the idea of customers manipulating the "MF'r" to accommodate the need for more fuel.

When you have time please post some pictures, would love to see your car.

Surfnsun, I still think I can get very very close to those numbers you just posted without removing my cats and mufflers. I have two, no wait, three more tricks left and I'm already creeping in on those awesome numbers of yours while still using the stock TPI setup and maintaining cats and mufflers.

FS

 

[SurfnSun]

My numbers were thru the stock TPI as well

 

[boostedmaxPSI]

My numbers were thru the stock TPI as well

In that case your 430+ / 570+ numbers are pretty low compared to what you actually had! That's truly impressive. You must really miss #48.

 

[SurfnSun]

Stop it....Im gettin misty. :cry






:L :L I would LOVE to buy #48 back.

 

[*89x2*]

In that case your 430+ / 570+ numbers are pretty low compared to what you actually had! That's truly impressive. You must really miss #48.

Don't get him going... :ugh

He carries a picture of that car in his wallet (still...)


That car is BADDDDAZZZZZZ! I still remember my trip to Orlando - the heck w/ Disney, I got the E-ticket ride in the B2K :cool

 

[*89x2*]

Great Thread!!!!

from the initial responses, it looks like 12psi is the norm. Hope more folks respond...

Callaway Owners - If you have dynoed your car, please share the numbers and what the specs were. If you do not want to disclose "everything" you have done, please at least post your dyno sheet(s)


Thanks!