Okay. I've got a 2001 Corvette coupe (not Z06) and it's now making 409 HP at about 388 ft/lbs of torque. It's got Texas Speed heads, been all reworked below, 42 lb injectors, Z06 exhaust, custom cam, underdrive pulleys and been dyno tuned by a great shop in OKC. I recently had an issue where the car was making about 370 on the dyno, but using oil to the tune of about two quarts per tank of gas (yes, really). I took the car in because the guy who built the engine for the previous owner had recommended a different cam but the owner had gone with a "Tsunami" cam despite the recommendation. My plan was to get this car ready for a supercharger... Well, it turned out that three cyls had bad valve guides, so they were replaced (cause of oil loss?) when the cam was changed. I was told the rocker arms were "too heavy" and might have hammered my valve guides, so at the mechanic's recommendation, these were replaced with stock stamped ones because he said these were what he used on 800+ hp motors. Now, with the old setup and despite the oil loss, the car ran pretty fast. The car now seems a bit quicker, but mpg's have dropped considerably (from about 22-24mpg to at BEST 14-15mpg on the highway) and it just doesn't seem to run very smoothly when cold (and at times once warmed up as well). Now, I'm not stupid or new to fast cars and I know that hp CAN come at a cost if not done right, but I was expecting that 410 hp was pretty conservative for these engines and would keep the car VERY streetable (as in, I can get in the car and run it everyday like a "stocker" without noticing any drivability problems), with just more performance when I wanted it. Instead, it seems quite "quirky" getting her going in the morning and not smooth at all when just rolling off from a stop light. To give you a better idea of how it's running, if I had just purchased this car as a brand new 400+ hp rated Z06 from the dealership and it ran this way, I would promptly return it with many complaints....yet people drive these cars from the factory just as you would any other car. My question is, was I expecting too much? Is this too "hot" of a setup without sacrificing drivability? What are everyone else's "daily driver" cars sitting at for horsepower and drivability? Any input is greatly appreciated. Thanks and sorry for the long post....

 

Title says it all. I would have someone else look at it. I am no expert but that is what I would do for the amount of money you are spending.

 

Seems as though you have gained some oil mpg, addressed your mechanical issues but lost gas mileage and a bit of engine civility. Time for a re-tune? Some may say a few more miles might let the electronics settle in a bit. Did you install NEW spark plugs after the oil consumption issue was fixed?

 

I would have someone else check the tune. 410hp should be extremely streetable, nice idle, good off the line, decent mpg, etc.

 

NEW CAM...................NEW TUNE. Do you have ANY DTCs. Investigate that.

READING YOUR Engine Diagnostic Trouble Codes (DTC)

This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.

The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.

Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.

There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.

Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.

Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.

If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.

Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.

NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.

These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs

Here are some very good sites that explain what DTC mean:

http://www.gearchatter.com/viewtopic11755.php

http://www.obd-codes.com/trouble_cod...d-ii-codes.php

Make sure to include the H or C suffix when you post your DTCs!!

 

Find a new engine builder and tuner.

 

Have your tune checked out. When I was NA, I made a little more hp than you have now (A4 unlocked) and it was fast, dependable, and got 26 mpg with a stall and 3.42 gears
Make sure the injectors were scaled properly, and the timing is high enough in the cruising range.

 

Quickly!

 

Every mod you make just makes a great car run worse. It came from the factory perfect. What a waste. If you want to go fast get an airplane.

 

My car runs great with all my mods....... Most of the time its not the mods, its who installs them.

 

Not really. The factory simply did a nice job of balancing performance and emissions. A simple tune can yield an increase in power and fuel mileage, but at a cost of emissions.

He simply had something go wrong with his mods and needs to go back to the beginning. Sometimes these things happen, just a poor engine build experience for the OP.

 

lol wow thats the funniest thing i've heard in a while

 

My vette goes faster than the last 2 aircraft I have owned. A hell of a lot cheaper to operate too.

 

Any time you alter air flow thru the engine, A LOT of the engine management tables in the PCM need to be changed or fine tuned to properly utilize that new air flow and cam specs. The Volumetric Efficiency (VE) table, MAF table and Power Enrichment (PE) table and Timing all need to be tuned. Until you do that, your NOT going to see maximum power or optimum efficiency (fuel mileage) TRUST ME,, Ive been there,,,several times!

Once you make sure that there are no mechanical or electrical issues, get a tune..

 

Good replies and I appreciate them all. I'm in the Oklahoma City area and have been using a guy who came highly recommended by one of the Corvette club guys I know uses him. As for the streetability, it seems I hit the nail on the head and this thing should be both fast AND tame. I'm kinda bummed because I've put a bunch of money in this car, and it's got a ton of bells and whistles to be running so poorly. Now I've noticed that my cruise control will not engage and I'm getting engine exhaust in the cabin from the recommended crankcase filter behind the left valve cover. This car had a nice aftermarket pcv system, but the builder seemed to think that this was part of my oil control issue. I'm taking recommendations for the best mechanics in the Oklahoma City area if you guys have any.... I'm taking it back to him to try and straighten it out, but if that doesn't work out, I'll need other options. Hell, I might even consider taking it to Texas Speed in the Spring if I have to. I went through this same thing with a '90 Vette and never could get it right, so I sold it. I just want a good, reliable car that makes somewhere in the 400-500 hp range..... This does not seem to be a tough mark to make with all of the 700-800 hp cars I see out there all of the time. I was hoping to add a supercharger to bring her into the 600 hp range, but with the car already running like this, that would be an extreme waste of money at this point.... Anyone know any great tuners in the OKC area that I can get a second opinon from?

 

By the way, should mention a few other running issues.... First, my coolant temp seems very low to me... It was 41 degrees last night and my coolant temp was 161 on the highway. I've NEVER seen it much higher than this, even on a hot day. I'm told these engines LIKE to run a little hot, so I was wondering if this was not part of the problem. Also, after running the car awhile, it still exhibits "cold engine" behavior like hesitation and stutter. Also, I've got engine fumes spilling into the cabin from a crankcase vent filter that was recommended by the mechanic. My question is, WHY would such a thing be necessary if the stock engines don't require it?? How does the stock system deal with crankcase ventilation and why won't that work for my engine. Also, on a side note..... For someone new to all of this computer-controlled tuning stuff, where is a good place to start learning it? Part of the problem is that the tuning parameters mean nothing to me at this point, so I wouldn't know where to start tweaking. I'm mechanically, electronically and computer saavy, but a programmed "tune" might as well be magic to me. I want to learn more about engine management so I have some clue.... What's the best way to learn??

 

Only FI engines NEED crankcase vent filters.

 

I first bought this book

http://www.google.com/search?hl=en&r...f200e8d6433b2a

then this DVD

http://www.summitracing.com/parts/SME-DVD-1/

this forum
http://forum.efilive.com/

PCM Tuning sections in LS1tech...

 

One of the first things people modding these cars do is install a 160 T stat. If you had someone do all the work or bought it from someone who did I would bet it has the 160 in it. You should also read this forum and do searchs on questions you have. I would look at the articles on PCV systems. Using vents on the valve covers with no other PCV system (I don't have any idea what you really have) isn't a good idea.

 

Thanks for the info. Researching the tstat and pcv issues on here now.....