After about a year of installing, working the bugs out and all that, I have a dyno appointment this Friday at my local speedshop. Rocky Mountain Competitive Research for those that are local to me here in Colorado Springs.

The short list mods are in my sig and in profile.

To recap, I have a Blueprint 383 that I installed a FIRST INJECTION TPI on this past spring. The engine was dynoed at 405 at 5500rpm, 440 ft lbs at 4400rpms using a 750 cfm Holley carb and 1 5/8 LTs. The FIRST TB claims to flow at 831cfms. I am using the Hooker 2210 LTs as described in my sig, which are 1 3/4 IIRC.

I understand that there could be a 15% loss at the wheels using the standard transmission. With that said, my calculations say that I should be putting about 348 HP and 374 TQ at the wheels. Now, I am at about 6000 ft altitude.

I will post results and the dyno sheet next weekend.

Guys, what are your thoughts on what kind of power I might make?

 

Interesting. Yes the altitude will skew the results. Maybe we will have to correct it to maybe 1000 ft or so.

 

If the dyno sheet from the builder is a true representation of what the engine will make with the carb, intake and dyno headers, assuming an out of the box FIRST, proper tune, a good free-flowing exhaust system, and typical drive-train loss,, if run on a DynoJet chassis dyno,, I’m going to guess around 330rwhp around 5300rpm and 390rwtq around 3900rpm with the standard correction factor.

 

Yeah 330's is about what I'd guess but dependant on how much loss is actually taken. I know 405 hp LS6's can engine dyno 420hp and put down 360-370 on the ground. 12% loss on the 6 speed and IRS rear. Auto is comfortable to assume 20% so thats 324whp with 405 hp engine.

Peak power probably wont be too much higher than 5000 rpm. I'm going to guess its at 4900-5000. torque I expect closer to 400 at the tires with TPI and 383 inches. Probably end up doing 375wtq

 

Thanks gentlemen for the replies and thoughts.

Posted are the Dyno sheets from today's event. Horsepower is a bit lower than I expected. 275 at 4400rpm. And Torque at 363 at 3400.

The speed shop noticed some AFR issues at 4500 and up. bit rich they said.

I hope to get it in their shop in the next month and get it tuned a little more accurate than the mail order tuner I used. Mike at RMCR thought I could get close if not a touch over the 300 mark on the Horsepower side with a tune thru them.

I have the stock Camaro airbox with K N filters. Might they be restricting some of those ponies. Would I benefit from the TA CA intake?

I am kind of disappointed that I didnt get to at least 330 HP... The torque is where I was expecting.

Any thoughts?

 

I didn't have any problems with the z28 snorkle (bottom cut out - if you haven't done that you need to) and K&Ns running mid 12s and shifting the FIRST at 5800/5600 on a 355 with a lot less cam than you're supposed to have.

Edit - The specs on that engine number says .487Int / .508 Exh & 234 Int / 244 Exh duration @ .050 - 112 degree lobe seperation. Did they use a different cam?

What chip and injectors are you using? Where did you have the timing and fuel pressure set? Did you try adjusting the base timing or fuel pressure on the dyno? If those are not the major "problem",, I'd make sure the catalytic convertor is not clogged.

However,,, I noticed it was a SAE correction. STD would be around 285HP and TQ around 375. If the shop thinks it could put down 300 SAE cleaning up the tune, that's about 310 - 312 STD horses with torque getting close to the 390 mark, making it off a little less than I would have guessed,, but the RPMs are off a good bit than what it should be doing.

 

The airbox has not been cut at the bottom like you mention... The chip is a tuned via email from Indiana ( I am in Colorado ) the memcal I am using is a stock V8 tuned fom Sinister Performance. The Injectors are 24lb Bosch 3s from Fuel Injector.com. The timing was set at 8* base and fuel pressure was 42lbs at idle. We did not adjust anything during the dyno. I will be having RMCR tune my car as soon as my finances allow, which i hope to be mid to late Feb....
I noticed that the rpms are off about a grand on both HP an TQ at peak numbers. Seems as if the peak Rpms were close to the engine numbers, I would be close on expected wheel numbers...

Might be worth mentioning that the car was originally a 5.0 TBI that was repinned for Speed Density TPI

 

If your engine has the 234/244 cam, peak TQ should be between 3700 and 4100 rpm and peak HP should be between 4900 and 5400 rpm with the FIRST. The FIRST really shouldn't effect peaks on that engine more than 400rpm due to the added runner length. If it doesn't make peaks at least at 3700/4900 something is going on other than a TPI style intake "choking it" - like maybe the converter.

First thing I would do is check the TPS and make sure you have at least 4V at WOT. I'm assuming you don't have a scanner,,, so I would put a timing light on the engine with her plugged up to see what kind of timing the chip had in it at idle. Get someone to help you so you can check the timing at WOT. Set the light on 34 degrees and see how close the mark is (before or after) right before he pops off the gas at 5000. Then unplug it to check the base timing. If its a 234/244 cam,,, I'd suspect it needs more base timing than 8 degrees (to hold min idle),, but a lot depends on what they added in the chip. Let us know what you found. I suspect it might need a little timing.

Next thing I'd do is open up the stock air box. Cutting the bottom out and removing the deflectors,,, if they're still in there, you might actually bring your AFR in line with the lower RPMs. In fact,,, there's a possibility with you gutting the air box and if it can take a bump in timing, you might need to increase your fuel pressure. Hopefully you can read the plugs.

 

Could be, but I am using a Magnaflow High Flow Cat that only has about 3000 miles on it. Installed it when the Maggie Catback was installed. And besides that joker is welded in anyway. Hopefully its not clogged like you suggest it might be.

I do have a data log cable and software, so I can see what those values are . I do remember when I was getting data for the tuner in Indiana, the TPS values were what they were supposed to be. .5-.6 at idle and 4.5-5 at WOT( TPS 100% ) Doesnt mean the TPS didnt move on me.

BadSS, Do you have the DATAMASTER program. I could send you the datalog session so you could see what its doing.

I will get the timing values you ask for and post them, because I m curious as to what they are compare to what I requested to be in chip. However, I do remember the datalog having the final timing being 32* at WOT.

I will work on gutting the air box. I actually was reading about that this past week. So basically, can just pull the bottom of the air box out of the car and just cut the baffles off of it ?

I could make some kind of "Ram Air" or "Cold Air" setup out of sheet metal or something similar to better force the air into the air box as well. I cant remember who it was I seen do that on the forum. I also heard about someone using dryer duct to do the same.

I do have another ? regarding the SAE and STD Dyno correction. What is the difference?

 

"The chip is a tuned via email from Indiana ( I am in Colorado )"


You need to start with a custom tune that is actually done on your car and go from there. If things are still not right after the custom tune you need to re-evaluate everything from the air-filter to the tail-pipe to see where there may be air flow restrictions.

 

Sorry,, I just have a hand held data scanner w/record for the OBDI and HPTuners for the newer engines.

SAE is corrected to a 77* and 29.6" and STD is corrected to 60* and 29.92". The difference in temp and pressure is about 3%. Most of the magazine use STD,, since it will give a higher reading.

Definitely gut the box and give some timing points. I'm thinking it'll take more timing that what you have,, which will help. The air-box and possible base timing "adjustments" just might put your fuel curve where it should be.

You know,,, I wanted to make sure I wasn't off on the RPMs I was saying it should be pulling,,, so I plugged the BP engine into a dyno simulation program. I tweaked with the unknown parameters,, like the head cc and flow (Vortecs with the 2.02/1.60 valves) and header length until I got it to match up with the BP published graph. I had orginally thought the heads on your engine might flow a little better than regular box stock Vortec heads (my excuse for my guess being off), but with the values I had to use,,, the program is saying they're not flowing much better than stock Vortecs. Then I swapped the intake parameters to match the FIRST and it flat-lined big time starting at 4400 rpm.

This curve looks entirely different than what the program estimated on my 355,, but my heads were larger and flowed more (on a smaller engine). Your results appear to be a physical limitation from the engine cubes, small head volume, limited flow, and the runner diameter and length. I think you can get the power up to where it should be,, around 330 rwhp (STD) without it dropping off as quickly as it does now,, but it looks like the peak RPM numbers may not come up more than 100 or 200 RPM of what you're seeing now. The good news as you can see with the simulation is the FIRST really boosted midrange torque - trading 20 peak HP for 40 peak lb/ft is not all that bad a trade off. Plus,, it should be a blast cruising around town even if you do have to shift the thing at 5000rpm.

 

So what kind of heads would be better all around than these "ported" Vortecs ? and still have the vortec intake bolt pattern so that i can reuse the vortec FIRST intake?

Just asking for food for thought. Possible future mod...

Anyways, back to the task at hand of gutting this airbox and getting this timing information.

 

build a 4" cold-air pipe with the biggest K&N cone you can fit and watch it pick up 20 to the tires. Those air boxes gutted still cost a stock LS1 over 15hp to the tires.

 

Timing with EST connected at idle was 15* and at WOT 31*

the Base timing was 9*

Fuel pressure with vacuum connected is 42lbs, and with throttle applied the pressure went down to 39-40 lbs... Isnt the pressue supposed to go up with throttle applied? Or am I mistaken?

 

The AFR 190cc Vortec SBC Eliminators would get the job done.
http://www.airflowresearch.com/index.php?cPath=24_117

 

I'd bump the timing three degrees and see how it ran. Check the datalog to see if it gives you any knock retard though.

Yes,, fuel pressure is supposed to drop with high vacuum and increase with low vacuum. What does it read when you unplug the vacuum hose from the regulator?

 

Your going alittle rich over 4000 rpm and way rich for n/a motor beyond 4500. Clean that air fuel ratio up and you shall see an extension of rpm range and a good bit more power. 300 should easily be in that setup with just air fuel ratio change which isnt bad.

Then play with timing and could see few more ponies but 31 at WOT is about where vortecs make power. They typically use less timing than other heads. IF you can have full timing come on quicker, you will pick up midrange power/torque. Make 30 degrees come in by 2800-3000 and it should fatten up that curve.

 

I know it is over a decade old thread, but very interesting! There was never a definitive answer to why the OP obtained such low RWHP.

I have been compiling data for different 383 strokers with different intake (Carb, HSR, Mini Ram, TPI, Super Ram, etc...). I came up this thread and was surprised no one had ever figured it out at the time.

Well here's my answer base on data collected and analyzed from other 383 set-up. There could be a lost of peak power for a TPI set-up between (8-18%) depending on TPI. 18% would be plain OEM TPI where 8% would be ASM or FIRST type.

Blue print 383 with 750 cfm Holley carb acquired by the OP (see chart post#1):
405HP@5500rpm
440T@4400rpm

It was a mild 383. You can easily push a 383 to 500hp in NA with dual plane & carb, but obtain only 460HP with a TPI for same set-up.

The OP installed a FIRST TPI intake and Dynojet it at 6000' altitude. He obtained (see chart post#5):
275RWHP@4400rpm
363RWT@3400rpm
As excepted, the peak HP and torque were moved lower in the RPM band due to the the long runner intake. Peak torque increased and peak HP decreased (all expected with TPI).

OP was disappointed as he was expecting at least 330RWH but more like 348RWHP. No one could really explained why.

My Calculation:
Peak HP with carb = 405HP
Peak HP lost due to FIRST TPI intake = 405* 0.92 = 372HP
Parasitic loss = 372* 0.88 = 327RWHP
Altitude factor for Colorado Springs, CO, 5994 feet elevation (-3%/1000') = 327*(1-(0.03*6)) = 268RWHP

OP obtained 269-275RWHP

For flywheel torque:
363/.82/.88 = 503 = 14% more than the Carb set-up which is expected with TPI intake.

Comments?