I'm an engineer by trade, I'm not really into dragging racing or having the baddest vette on the street, what I do admire is efficiency and design refinement. I've got a bone stock 2001 C5 base convertible. What I would like to do with it is just address some of the design shortcomings for a mild boost in horsepower and an overall increase in efficiency of the LS1 by making small improvements in the stock design without modifying any of the engine internals or adding headers. From what I've read, these are the basic design flaws in the car's engine:

Restricted intake from the airbox through the throttle body
Restricted exhaust and badly designed H pipe
Fuel injectors do not deliver enough fuel
Engine programming

If I'm missing any, please let me know.
I could use some advice on the "Restricted intake from the airbox through the throttle body" remediation. I was all excited reading about Callaway's Honker/Throttle Body/MAFs upgrade and then I discovered they quit making the throttle body assembly. Is there similiar quality set up out there?

On the exhaust it looks like the most favored is the Corsa Extreme cat back series, but on the X pipe, it looks to me from what I've read if you used the Borla X pipe with the Corsa you'd get better flow. Any reason this is a bad idea?

On the fuel injectors, these look very interesting http://afispower.com/products/fuel-injectors/ but I cannot find a single review of them anywhere. Has anyone used them?

On the programming modules, I am totally lost. I just want better performance from a stock engine with those improvements. Is there any one preferred for that?

Thank you for your time!

 

Stock fuel injectors will support 400rwhp, you will not gain a thing by changing them. Catback exhaust systems with a x pipe might gain you a single digit bump in power, combined with a cold air intake a few more. Tuning the PCM using software like EFI LIVE or HP tuners is the way to go

 

Beware bolting on or removing hardware may affect your emission controls and cause problems in states that require emission testing during your required inspection. Some folks actually remove performance mods just to pass the test all for a couple of horsepower they don't really need.

 

If not interested in headers, the best bang for the buck efficiency impact, I'd not do much else.
Stock intake isn't perfect, but very little to be gained by replacing it on a stock LS1. Maybe pop some holes in the cover or buy a used Z cover. You might gain 5HP from intake.
Muffler system is about sound mostly. Again, you might get 5HP from an aftermarket or Z system.
Injectors are fine. There's a reason why you can't find reviews.
Get a tune? Yep, after any changes you do, particularly if you have an auto.
An X pipe design is generally preferred, but again sound is the biggest driving factor.

 

There is sooooooo much on the table that can be improved both efficiency and power wise by a tune. In many cases it's proven more so than spending hundreds on CAIs, cat-backs, and whatever else that barely marks a notch on improvement. Plus it's 2018; there's not a whole lot re: LS that is any sort of sorcery or unknown.

You best bet is to 1) either get into contact with a local tuner that can give you a tune to improve efficiency and power (it can be done with a tune), a good local club is a good resource for this as they'll likely know who to go to or 2) get something mail-in that's already prime for this sort of thing like the COW tune.

 

The big difference in power vs efficiency tuning will be sticking with the factory temperature thermostat instead of the go to 160* thermostat. You could probably lower the fan settings 10 or 20 degrees without hurting fuel economy though....

 

Don't you have a shuffleboard game to go to?

 

Your engine is a very good engine, It serves the needs of many owners. If you can sacrifice a little gas mileage; your best bet for the seat of the pants, is a 315 or higher rear.
Good luck.

 

Moved to C5 Tech.

 

You can piece it together like I did (and then sold it because the mod sickness is real) https://www.corvetteforum.com/forums...ower-duct.html

 

The only way to make any additional hp thru the air intake is to have outside ambient air going to the MAF, the changes to the air intake using engine bay air will not change anything. Cooler air is more dense so more dense air can get into each cylinder per engine stroke. There are several good outside air intake systems on the market like Callaway, Ice Box, VeraRam, Halltech license plate cover system, etc.

The PCM has an adaptive strategy (non programmable) GM put there based on the stock engine, adding larger inputs of air before the MAF actually slows down the movement of the air that is being measured so the engine will run leaner. Some overly rich engines may have a slight benefit but most do not. The stock air cleaner was designed to support an easy 350 hp so adding another engine bay intake system brings nothing to the table except maybe a filter that will get dirty easier because it is not as efficient as the stock one.

Bottom line, the outside air intake system and a good scan/log tune will maximize the efficiency of the stock LS1 engine. The advantages of the scan/log tune are not in the max hp but in maximizing the 2000-5000 rpm range efficiency and acceleration. On the exhaust side, changing anything after the cats will only change the sound of the engine--many feel this is a great improvement.

Our local club, being in Detroit, had several engineers who worked the the tech center or proving grounds and they used to laugh at all the hp claims vendors would make for their products. We had one member who had a 2000 Corvette who believed all the early hype, since he liked to drag race he would buy almost every new hp adding product on the market. On sping he mentioned over the winter he added about 20-22hp with those product. When he went to the drags, his trap speed was still the same and his ET's were about the same also.....he finally became a believer that it was all hype.

 

Pretty limited mod list...

Fresh tune up
LS6 intake
CAI
Dyno tune for speed density (remove the MAF all together if you feel it is a restriction) Measure MAP to see reduction in intake restriction.

Efficiency is getting more air in and more air out easier...headers and a tune will be best bang for the buck. Catbacks and catless midpipes (for the cost) will not do much for you but add noise.

 

Cool air and thermostat temperatures make power
Warm air and thermostat settings make mpgs

ps sounds like the member in question slapped all the bolt on parts on his car and never took the time to get a proper tune....

 

Define "efficient". Are you talking gas mileage, horsepower increase per dollar spent on mods, what?

 

I liked your post, like others here you recognize that efficiency and power are not the same thing and make your point very well. Improving efficiency to me is that for the same X centimeters of gasoline I increase either mpg or horsepower by making improvements to the way inputs and outputs are managed by the system. Improving power on the hand, may mean you really don't give a sheet about X. Usually the easiest way to increase efficiency is to reduce friction in the components that input air, atomize fuel or output exhaust, but what you seem to be saying is that in the case of the current design of the Ls1, all the claims made for the polished TB's and replacement of the accordion bellows connector "in order to reduce friction" of the air flow and exhaust modifications "to reduce power robbing back pressure" (to quote the vendors) are essentially unsupported by track results. It makes sense though, because pretty much everyone here emphasizing the tune are going to the heart of it, because at the macro level, that is indeed where inputs and outputs are being managed, but instead of managing friction, the key is to refine the software's management of inputs and outputs because friction and restriction are already managed well in the stock design to the point that there are no real design flaws to overcome, and that the actual design flaws are in the stock programming.

This whole thread has been very enlightening, you guys are great! So essentially, what the general consensus here appears to be is that lowering the ambient air temperature of air going into the LS1 engine and a tune is the only thing that results in a net gain in efficiency on a stock LS1, that all the other bolt-on modifications and fancy injectors being sold are useless unless internal modifications such as bigger cams, force induction and/or head work go along with it, otherwise, it's just wasted money. My question there would be then, why so much hype on changing out intake manifolds? No gains there either? I have read big claims for changing out the LS1 intake to the LS6, but I also had someone tell me that in 2001 they started fitting the LS1 with the same intake as the Z06, is that true?

 

cool air = power
warm air = efficiency

Yes, somewhere around 2001 the base model c5 started using ls6 intake manifolds and short blocks.
I believe some of the added ls6 intake manifold power was offset by adding two "pup cats".

 

Usually efficiency is defined as the best use of inputs into the system that cost money, since in the case of the internal combustion engine that is gasoline, improving efficiency is that for the same X centimeters of gasoline I increase either mpg or power (horsepower or torque), which means I get a return on my investment in modifications in either time or money. Perhaps I should have been clearer on that in my initial post. Ideally you want to increase either one or the other without sacrificing either or find the maximized mid point where neither can be increased without sacrifice. From an engineering standpoint, if your consideration is increasing power alone, you can usually do that most easily by increasing fuel inputs, but if you do that on a stock engine you run the risk of getting outside of the design envelope, and blowing things up, something many an 18 year old with a spun bearing in his two-four barrel Camaro on a stock engine experiences. So when you install say, forged pistons for example, you are really just increasing the size of the manufacturer's design envelope so you can burn more fuel or run more powerful fuel.

Mathematically, it's a measure of how much work or energy (again in this case in the form of gasoline's energy content) is conserved in a process. In any process, work or energy is lost, for example as waste heat or vibration. Efficiency is the energy output, divided by the energy input, and expressed as a percentage. A perfect process would have an efficiency of 100%, in other words, in a perfect world, all the energy of the gasoline would be directly transferred to the wheels, but that is not the case, some is lost to friction, some is lost as heat, some may be lost as unburned fuel. The idea is to reduce those losses and convert them into usable energy.



https://simplicable.com/new/efficiency-formula



..

 

OK, the measure you're referring to is BSFC, Brake Specific Fuel Consumption. This number measures the amount of fuel in pounds needed to produce one horsepower for one hour. And contrary to what you think, most mods, including big cams, modified heads, and the like, IMPROVE this number. That's because they increase the efficiency of air moving through the system. NASCAR engines are actually way more efficient from a horsepower per pound of fuel standpoint than a stock corvette because they are not held back by cost, emissions, or noise factors.

And where do you get the idea of reducing "friction" of the air moving through the system? What kind of engineer are you, anyway? The idea of intake manifold and exhaust manifold design is based on wave dynamics, not reducing friction. I suggest you read David Vizard's book, . It will spell this out in a lot more detail, as well as telling you WHY tuning the computer, even on a stock engine, builds power.

When you first start out modifying your car, there are two ways to improve performance: Improve the airflow through the engine, and reduce the manufacturing variance of the various parts of the engine. You've seen everyone's responses on improving airflow, but you're making a mistake leaving out headers. While they require the supporting mods of free flowing intake and exhaust, they will make the biggest difference in terms of airflow because they introduce pulse scavenging to the exhaust system.

You'd also be mistaken in leaving off fuel injectors. While the stock fuel injectors can handle the fuel flow requirements just fine, GM keeps costs down by not flow matching the injector sets on each engine. They come from the OEM flow matched to +/- 10%. Most aftermarket places will flow each injector individually and put them in matched sets that flow to within +/- 1%. This allows much finer tuning of the car's computer.

There are lots of places to improve efficiency on a basically stock motor. For example, GM is known for using the lightest valve train parts they can to help meet fuel mileage requirements. However, simply replacing the pushrods and valvesprings on the car with stiffer components, even if you don't swap out the cam, can net 10-20 horsepower simply by improving valve motion control.

 

If you are planning street boost of about 6 PSI or less I would keep the stock MAF and T-Body----There is really NO advantage by going to larger ones unless you plan on full time racing and expect to runn the engine above 6500 all the time
The stock MAF and t-body are good to 600 crank HP as an average To test this you would need to data log your MAF table and see if you exceed the table--If you do then go MAFLESS or get a larger MAF As for the T-Body like I mentioned a larger one is typicallly not required unless you plan on running 6500 RPM most of the time and are not worried about low RPM TQ It is just like putting a too large of a carb on an old school engine--Yes you may gain soem topend HP at the cost of bottom enf HP and TQ and throttle response
INJECTORS Industry standards say not to exceed 80% duty cycles Again only by data logging them you can see where you are---As mentioned there is NO HP advantage by going to larger injectors unless you have outgrown your stock ones----If you deem you need larger ones don't go crazy as too large of an injector is hard to tune and clean up at low and mid range RPM's--
Remember that a duty cylce of 100% means the injectors stay open ALL the time--Not good !