Supercharged your LS Engine? Any regrets

[mechatron]

Rather than spend those sort of dollars on heads, you would be far better off forging the bottom end and keep the heads you've got (just lower the compression with dished pistons) then you could happily crank the boost to 15 psi reliably.

Just put a 2300 blower on what you've got, if you get bored and want more, forge the bottom end and swap pulleys for more boost.

a couple of pounds of boost is going to make more power than a $5k set of heads...

Great idea thanks John. Any idea what the cost of forging the bottom end would be?

[Diggler]

Great idea thanks John. Any idea what the cost of forging the bottom end would be?

8 hours motor in and out, 10 hours at the engine shop, plus parts: pistons $1000 + rings $200 + billet con rods with upgraded rod bolt $825.00 + CompStar crank $1200. (Your cam is really not suited +$750).
That's retaining most of the other bits you have, before cost of blowing it.

OP perhaps review the specific result you chasing rather than transforming your (unoptimised) setup into a blown motor. How are you getting 11:1 static at the moment, and what other tuning mods have you already? Do you have a recent dyno graph to better discuss where you are at and realistically where you would prefer to be?

I'm sure you know how it goes... you can't always get what you want but sometimes, you just might find, you can get what you need. Simply, for less.

[Diggler]

I assume from your original post this is a daily street car not a race car, just sayin' that without much effort from where you are at, GenIV heads: even with more moderate cam and gears will slay almost every charged (maggie and ProCharged) stock bottomed GenIII well past 200kph, happily daily commute, and get 11s all day. This 6.0 does that with low lift with the AFM contraption active:



Consider that more HP with FI is likely not what you need, nor want in practice. A better thought through cam may be the key ($750), LS3 heads and induction (64cc CNC assembled all good bits) is $2950, plus manifold & TB ($350) 5.5 hours in an out. Tuned properly ($600). Upgrade cost offset with sale of your current high performance heads of course.

Depending on your location you could possibly spec cam and tune to e85 and run true hi-comp - pay less in fuel and get ~ same power and torque as above.

[ls2 cruiser]

Diggler, only problem with fitting gen iv heads on a ls1 is they don't fit the smaller bore. I would think that a cammed ls1 with head work is less of a nice daily driver in comparison to a blown ls1. In my opinion a blown ls1 will beat a cammed ls1 any day, everything else the same like gears etc. I have seen the blown gen iv cars race the cammed gen iv cars at willowbank. Same tuner and mechanic - elite automotive. The blown cars went better.
Of course the blowers are expensive and are a rip off as far as price goes in Aus, but the big benefit with power is they have full torque much lower in revs and hold that torque through to the normal torque range. The torque they create is higher than a N/A engine in most cases as well. A good tune is the most important thing with a blower. I have seen a gain of 100hp on my engine just by changing timing only one or two degrees in the timing table though the rev range. The feeling of the greater torque coming on early in revs is where you get the noticeable difference when driving on the street. It really does set you back in the seat.
The standard ls1 bottom end will handle the 1900 at 9 psi without touching it. The only weak spot is maybe the rod bolts which could be upgraded to ARP 2000 rod bolts. If you are going to forge the bottom end of any engine you may as well go bigger in cubes and change to a 6 litre or 6.2 litre block to start with, but then again it depends what outcome you want and how much you want to spend.

[mechatron]

Thanks Diggler, just a few things. My car isn't a daily driver but it's far from a race car. Engine has the 220 cam, Comp lifters, Trend Pushrods, Dual valve springs & ARP head bolts. The heads are just the standard 241 heads that have been decked (to give 11:1 comp) & cleaned up. Don't get me wrong my car goes very well...nice and torquey in the low to mid range section but I just want more. I want to be pinned in my seat and struggle to change gears. Last time it was on the dyno (2yrs ago) it pulled 391rwhp. See the graph below:
ImageUploadedByTapatalk1412858332.007590.jpg

[offshore]

Thats a nice power curve. Sams obviously set that up for you well. Id have a chat to Sam about swapping your cam for a blower cam if that one isnt suitable and see how he thinks that compression will handle some boost or maybe exchange your heads for some higgens cnc ones cheaply for flow as well dropping the compression. He might have some hanging around there and do you a deal with the blower who knows. Thats the best way forward I reckon the blower is the way to go for some fun and you obviously want one. You can probably get a 2nd hand blower to save some money if you have to.

[Diggler]

Got it, you have a 5.7 and you want torque, not horsepower. That brings me to the dyno chart...

Last time it was on the dyno (2yrs ago) it pulled 391rwhp. See the graph below:
ImageUploadedByTapatalk1412858332.007590.jpg

Don't view the above chart as a standard measure of output, because it is not, else your 5.7 gets more torque at the wheels than a 454 gets at the flywheel, or exactly the same as an LSA...

If 754Nm at the wheels is indeed the case that would sufficiently pin you to the seat, but before you spend another cent check the veracity of the torque scale shown in the graph as you need to know where you are at with your current setup on 98.

What transmission and diff gears?

[Diggler]

If chart is where you are at then you won't get much more than 750Nm below the entry price of used MP1900 and thicker gaskets.

[white lie]

Rear wheel torque will always be higher than flywheel torque. It's multiplied by the driveline gearing and tyre size.

Most blown combos will be closer to 1000Nm at the wheels.

[offshore]

Blowers have way more torque they flatten the torque curve which means you end up with buckets of power every where normally aspirated motors dont get a look in for general street duties. At the drags when your always in the top end power it doesnt matter as much.

[Diggler]

Rear wheel torque will always be higher than flywheel torque. It's multiplied by the driveline gearing and tyre size.

Most blown combos will be closer to 1000Nm at the wheels.

Silly to say that, of course gearing affects torque, gives totally incorrect reading, is why is J607 and J1392 assumes 1:1 transmission ratio before final drive. BTW most blown combos that state 1000+Nm atw via GM '80 or '90 box (including the new 8L90) are wildly overstated and incorrect. Please provide some examples for me to illustrate for you.

My point is that chart does not use standard 1:1 calibration to compare trans input rpm to trans out rpm as per standard practice, which in terms of absolute quantification for a standard comparison, is a useless document.

[mechatron]

Thats a nice power curve. Sams obviously set that up for you well. Id have a chat to Sam about swapping your cam for a blower cam if that one isnt suitable and see how he thinks that compression will handle some boost or maybe exchange your heads for some higgens cnc ones cheaply for flow as well dropping the compression. He might have some hanging around there and do you a deal with the blower who knows. Thats the best way forward I reckon the blower is the way to go for some fun and you obviously want one. You can probably get a 2nd hand blower to save some money if you have to.

Thanks Offshore. Also I should have been clearer before...Sam didn't do this combo....another workshop did but Sam did the final retune.

Sam actually hates this cam since it has the aggressive XER lobes and as a result it's very noisy. I myself like the noise

And yes Diggler that's rear wheel torque so the flywheel torque has been multiplied due to the 3.9s in the rear. Also my car has the normal T56 manual gearbox. Wheel size is 19" (245/35/19).

And as offshore stated, I'm looking to getting a flatter torque curve and more of it. Closer to the time, I'll speak to Sam and I'm sure he'll be able to find me a good set of 2nd hand 241 heads with standard compression. As for the blower I'm not keen on buying second hand as I've been burnt before buying 2nd hand

[offshore]

Im probably taking my car to Sams for a check in Nov and he'll hate my cam to as it got the really aggressive LSK lobes but it makes power so im happy. But i might even get him to swap it out and say to him if you can give me more grunt with your cam go for it!

[mechatron]

Im probably taking my car to Sams for a check in Nov and he'll hate my cam to as it got the really aggressive LSK lobes but it makes power so im happy. But i might even get him to swap it out and say to him if you can give me more grunt with your cam go for it!

Sam's a straight up honest guy so he'll definitely tell you what he thinks. As for my cam it sounds really tappetty as if I've got noisy lifters...but its just the profile of the cam.

[Diggler]

Firstly let me say that I think you can get what you want for not much effort once you have correct facts.

What transmission is it and wheel/tyre size please?

Indeed the raw roller torque figure is a real measurement of output, just like if you logged in first gear, second gear or otherwise. However it is not torque derived from Motive Force on a Mainline dyno, which is what you need to put your current engine putput in perspective. Your chart doesn't provide a calculated value based off RWKW and Engine RPM, Mainline's “Derived Torque” takes any gear multiplication out of the equation, so one very good way of using Derived Torque is, if you have a particular car that had 3.46 diff gears, and has now been changed to 3.7, the Derived Torque value will not be affected, whereas the Roller Torque will, due to the fact the overall gearing of the car has changed.

Peak Motive Force is 1556 Lb @ 134 kph, so given known diff ratio we can derive torque once the type of transmission and wheel dimensions are taken into account travelling at 134kph. Your chart lacks the requisite inputs, simply logs roller torque for that run.

I realise you want a new blower OK, but that is a lot of work and outlay when it may be entirely possible to get pinned to the seat with slight modification.