95z28man

My 383 build was just dynoed on the engine dyno and it made 454hp. The shop built it for some nitrous use down the road, so the compression is slightly lower than it should be for N/A use (I don't have any numbers from them yet). I didn't get the torque numbers or RPM's yet either, they just let me know the hp so far. 454 seems kinda low to me for the crank power, even with the lower compression. My question is, do shops usually just build the motor and dyno it first to get some numbers, then do all the tuning on the chassis dyno? I was told that when it's all said and done there should be at least 500hp at the crank, so should I be seeing some bigger numbers after they chassis dyno it? I'm assuming I will because obviously the computer is on the car and thats where they get most of the tuning done and I've heard many guys pull 50hp just from tuning alone. With 454 now, I'll only be seeing a little over 360 at the wheels and I wouldn't be too happy about that.

BTW, I talked to them on the phone and they just gave me an update with it and I didn't get a chance to ask them about it, so I'm just kinda looking for some input here before I go in on Monday and see everything myself and then ask them.

SS RRR

Detailed mods list would help greatly to help answer your question.

95z28man

I don't have any flow numbers or cam specs yet. Every single part is all new, except the block which is converted to 4 bolt mains and refurbished.

I'm more or less just trying to figure out if this 454hp will be able to be tuned up quite a bit, since I was told about 500hp would be at the crank, equating to about 400 at the wheels. As of now, I probably won't have much more than 360 to the wheels. So basically I'm hoping that they have just built the engine and simply dynoed it for some numbers and then will tune more power into it. I'm posting here to hopefully have someone who knows, confirm that for me.

Like I said, I'm going in Monday and will ask them when I get there, I'm just trying to get some peace of mind here hopefully...

Injuneer

Why do you feel you will have 20% losses through the drivetrain? If you added info about your car, as SS RRR suggested, it would help. We don't even know what tranny you are running, so you flywheel HP to rwHP conversions are confusing.

Your comment about building it for nitrous, with "lower" compression seems odd, since that's not the way to build a nitrous motor. Nitrous loves compression. If you are going for a heavy hit, the pistons may be heavier, the ring pack may be dropped down a bit on the pistons, reducing stability and cost a few HP, the cam LSA may be higher, helping you on the bottom end, but not promoting high "peak" HP numbers. But lowering compression for nitrous isn't correct.

When they ran it on the engine dyno, what did they use to control the ignition and fuel injection, if your PCM is still "in the car"? Did they run it with full intake and exhaust components, and all accessories operating? If not, you're probably going to take another hit when they put it in the car with the accessories and use your intake ducting and exhaust. Still wondinering how they tuned it without your PCM. Do they do a lot of LT1's, in which case the may have an LT1 PCM available?

95z28man

I'm probably wrong about what I said with the compression. It was explained to me once back when I started the build so I'm not too clear on it. I really don't know exactly how they dynoed it yet, I only got the hp number. They have done quite a few LT and LS motors but I'm not sure if they have the PCM available. I CAN tell you that when it goes on my car it will be run through a Performabuilt level 2 4L60E w/3200 stall, stock driveshaft and rear. Car is full weight as well. They have a Dynojet chassis dyno. My exhaust is complete from LT's, y-pipe, loudmouth, no emissions.

I'm not asking anyone to tell me if my hp numbers are "right" for my mods. I'm just wondering if a shop will typically save the real tuning for the chassis dyno, over the engine dyno. The reason I'm asking it because I only made 454hp, but was told it would be closer to 500hp and I've heard of people gaining upwards of 40-50hp simply from tuning. I'm hoping this is the case here, so when it's all said and done, I really will have 500hp at the crank.

BTW, I was just using 20% loss because I read that that is a "typical" percentage loss.

Thanks so far guys, I know I'm being vague, but that's because I, myself, will get all this info on Monday when I go in the shop.

Injuneer

Without knowing what they used to control the engine on the dyno, its impossible to tell you what will happen when the engine goes in the car. When my engine was built, the shop had the same aftermarket ECU in the engine dyno cell that I was running in my car. They did a full tune to optimize NA, 1-stage nitrous and 2-stage nitrous. The test setup included the full intake and exhaust, and limited accessories. When the engine went in the car, they ran it on a chassis dyno, and I got all the numbers I needed to calculate actual drivetrain loss for each stage of operation. Then they did some fine tuning on the chassis dyno, but nothing dramatic.

Even then, its still not necessarily optimized for the real world. It has to go to the track for further tuning. I think you may be focusing far too much on a single point dyno result. You have to look at the entire curve, and optimize the area under the curve for the specific RPM range that your car will see on the track. Its not all about peak HP on a dyno, and that number will not guarantee you a specific result on the track.

95z28man

Injuneer you're right about that. I am focusing too much on that, I went in hoping for around 400rwhp and even more torque. Which is still possible I guess. It's just when I called and they told that number I was pretty disappointed. I mean, I installed my own heads/cam on that car with the stock block, and it put down 360rwhp but the bottom end let go before they were done tuning. I decided for them to rebuild to a 383 built for nitrous to accomodate future plans... and now I hear it only put 454hp on the engine, which IF a 20% drivetrain loss occured, would put me VERY close to the SAME numbers I made with the stock block and a smaller cam. I would be kicking myself if that happens.

SS RRR

Don't worry about what one dyno states. So you don't even know what mods you have in your engine?
Who did the build? Wouldn't be Burtonsville Machine by chance would it?

Injuneer

Through an auto or an M6? M6 will only lose about 12.5% at that HP level. I'd suspect a 4L60E would show about 16% loss, and I know a TH400 with a loose, non-locking converter is good for 20-25% losses.

96capricemgr

Tough to say what the drivetrain losses will be. One supposedly reputable LT1 builder(who advertises here) sells engines that in the HP you got would only put about 330 or so to the wheels as his 440hp package only put 32x down and his 520 package never seems to manage 400 at the wheels and as low as 370. Call it a happy dyno if you like.

I second Fred's comment on the "lowering compression for nitrous". Don't second guess yourself so much a LOT of shops out there do stupid things liike lowing compression for nitrous and a LOT of "built" LT1s make less power than if the heads and cam were run on stock shortblocks. I have a real suspicion that you just choose a terrible shop who did not understand the LT1. I hope I am wrong and this is just all some misscommunication or the like and that the engine does run well for you. I have just seen too many bad builds to be optomistic given what you have shared.

Injuneer

Let's go back to step #1, or you will never get close to a meaningful answer.

You had a 383 built. You have no idea what parts were used.

What did you tell the builder you wanted him to build?

Did you specifiy a peak HP level?

Did you provide him with your budget?

Did you explain your priorities, with regard to emissions, "streetability", intended use (stoplight drags, track only, combo of the two), etc?

Who did you expect to "tune" the engine - self, mail-order, chassis dyno?

Did you provide any of the parts, specifications for any of the parts (e.g. - brand), or did you let the builder choose all the parts?

How much nitrous did you tell them you wanted to spray?

Without this info, any further discussion is really pointless.

95z28man

And just to add some more info, Performabuilt Level 2 4l60E auto tranny w/3200 stall is being put in as well. The stock rear is being used, but the previous owner may have added 3.73's because my original tune put the speedo off when I sent in 3.23's as the gear ratio.

95z28man

Nope. Racekrafters is the shop name, they have a website you can google if you want to.

I hear you on that. I'm hoping that's not the case here. They seem to a reputable shop and are the only ones I know of in my area with a Dynojet. So hopefully all turns out well, or else I no longer have a good shop to go to.

96capricemgr

Like I said "reputable" shops still turn out under 400rw out of supposedly 520flywheels motors. Reputation means less the more I learn. Also understand that some shops give a few customers parts to get a good reputation, find someone who has a shockingly fast bolton car and give the guy parts and the car will still go faster even if the parts are junk. Some individualys put a LOT more into wringing a car out than most of us do and in those cases they make bad vendors look good.

Might I suggest going in monday with a list and take notes, otherwise it will be easy to miss a detail.

95z28man

You can count on me going in and getting all this info. It's my fault for keeping myself in the dark too long. I basically left most of this up to them without questioning too much. The thing is, they never actually guaranteed me any certain hp or torque numbers, they just told me it SHOULD get close to 500hp N/A. But the more I think about it, my number so far isn't all that bad assuming Injuneers guess at 16% loss is more accurate than my 20% guess. With 16% loss I'll be over 380rwhp which isn't terrible, but the torque should be signifcantly higher, which I'll find out tomorrow.