Odd Dyno Results

[Bullitt]

I converted my car to EFI not too long ago and only recently got a chance to get it on a dyno to see how it's doing. Here are the basic specs:

306 w/ ~ 10.5:1 compression
TW Heads (upgraded valve springs), not ported
Lunati roller cam 51017
Victor EFI intake
30 lb/hr injectors
Pro-M Mas-Air sensor (76mm)
70 MM Throttle Body
Longtube 1 5/8" headers
3" x 2.5" X-pipe with 2.5 flowmaster pipes out
MSD 6A box + HVC coil
Stock Ford Distributor / TFI module 14 degrees initial timing
A9P computer (no chip)

I've posted both dyno runs, 1 from before with the carb and 1 after done today. The carb setup was the same as the above except for a Performer RPM intake w/ Edelbrock Carb (750cfm) and MSD Billet distributor.

They were having issues with the dyno today so I only got 1 pass. They could only read HP off the drum since their RPM pickup wasn't working (hence the attached chart is interpolated from the HP printout I got).

Thing I'm confused is why the car doesn't seem to pull at the top-end like it used to. I'd think with the Victor EFI it would run as well up top as the old carb setup did, but that isn't supported by the dyno chart... Is it possible that maybe the stock Ford distributor isn't cutting it at high RPM? The car was taken all the way to 6200 RPM, but for some reason data didn't show up...

Any thoughts? Thanks!!

 

[88mouse]

What was the air fuel ratio?

30lb injectors seem pretty big for a 306.

 

[Bullitt]

Air/Fuel Ratio wasn't working unfortunately.

Based on the old carb numbers with a Victor manifold (not reflected in that chart) it was doing 335 or so to the wheels which is near 400 at the crank and about right for 30lb/hr injectors.

 

[5spd GT]

Looks like it is camshaft related by not matching the current set-up.

 

[Bullitt]

Looks like it is camshaft related by not matching the current set-up.

I'll look into that since the current cam was discussed and picked on the phone with the Lunati tech guy based upon the original carburetor setup.

Also going to look into the ignition some, wouldn't be surprised if the Ford distributor isn't all that great for high RPM use...

 

[88mouse]

I got some what the same setup as you. This weekend I swaped my pro product intake out for a holley. Had a set of 30's and a meter for them. So I put them on to. Car didn't run worth a ****. They where just to much for it.

 

[machstang23]

What was the air fuel ratio?

30lb injectors seem pretty big for a 306.

I got some what the same setup as you. This weekend I swaped my pro product intake out for a holley. Had a set of 30's and a meter for them. So I put them on to. Car didn't run worth a ****. They where just to much for it.

I don't think 30#er's are too much for a 306. I have 30lber's in my 306 and it runs like a champ (AFR 185 heads, and RPM2 intake, f-303 cam) haven't had it on a dyno yet, but it runs and idles great, and I have good street manners as well... as someone mentioned above, I would look at the cam being the culprit, but I would think that with the Victor intake your running it needs more RPM then 6200 (more like 7000ish) to provide the up top power your looking for.

 

[Bullitt]

I just find it odd that it would pull to almost 7000 with the old carb intake, but with EFI it seems to be running out of breath. Not ruling out the cam, but just seems odd to me.

While they didn't have wideband on it, I think it might be running lean as the headers got hot and burned off some stuff that regular street driving hasn't. Going to look into an adjustable pressure regulator and a dyno that actually has a working wideband...

 

[Rick James]

I dont see how any presumptions can be made until you get it up on a dyno and tuned.Can anybody give an explaination to why they think its the cam?If the a/f ratio and ignition timing are wrong , the engines not gonna run right period.Doesnt matter injected or carbd.

 

[NIKwoaC]

I dont see how any presumptions can be made until you get it up on a dyno and tuned.Can anybody give an explaination to why they think its the cam?If the a/f ratio and ignition timing are wrong , the engines not gonna run right period.Doesnt matter injected or carbd.

Intake design, particularly runner design, greatly affects how an engine performs and where it makes its peak torque in its operating rpm range. While there is a lot that goes into it, lets leave it at this: the length and cross sectional area determine intake air velocity and the speed intake air pressure reverberations move (due to the closing valve events) at a given RPM. A cam should be ground to cooperate with the intake design (among other things) to properly take advantage of the runner design to make sure the valves are opening when intake air velocity is highest right at the cylinder head and the most amount of air/fuel can be ingested into the cylinder at the fastest rate.

This being said, the carb intake manifold is going to have much different design and thus, different operating characteristics than the EFI will, that is why people here are suggesting the new cam, a cam that is ground specifically for the EFI manifold.

Take a look at this article I just pulled from the Google machine. It has some pretty good info on the effects of runner design without really getting into the formulas and physics behind it.

Intake Manifolds: From Mild to Wild: Engine Builder

I agree with what you said about tuning the car. It sounds like the dyno in question was on the brink anyway. And am I understanding it right? Did the car only loose 10-15 HP after the EFI conversion? I imagine you could make up that loss with just a tune, and maybe even gain some after a new cam.

 

[Rick James]

So your saying a cam needs to be ground for the intake being used?i always thought a cam was ground to compliment the intake and heads as a whole package.Your article is about intake designs,if you look at his old set-up with a carb he used a performer rpm(1500-6500 rpm band).Now he is using a victor efi(4000-7000+rpm)if you go with the questionable dyno results,it looks like power drops off around 5500rpm or so,so do you think that intake is really gonna work with the current set up?I have a feeling with a tune and PERFORMER rpm efi intake he should put down similar #s to the carb set up plus a wider torque curve.Now If he wants an engine to pull to 7000rpm+ then yes he has to get a cam.

 

[Rick James]

Bullitt is this a street car or drag car?

 

[NIKwoaC]

So your saying a cam needs to be ground for the intake being used?i always thought a cam was ground to compliment the intake and heads as a whole package.Your article is about intake designs,if you look at his old set-up with a carb he used a performer rpm(1500-6500 rpm band).Now he is using a victor efi(4000-7000+rpm)if you go with the questionable dyno results,it looks like power drops off around 5500rpm or so,so do you think that intake is really gonna work with the current set up?I have a feeling with a tune and PERFORMER rpm efi intake he should put down similar #s to the carb set up plus a wider torque curve.Now If he wants an engine to pull to 7000rpm+ then yes he has to get a cam.

Yes, it does need to be matched to the whole package (that's why I said earlier, "among other things"), but once a component is changed, the others need to be rethought. In this case, he probably needs a new cam, and even if he did step down to a milder EFI intake, he still probably needs to reconsider his cam options to get the most from his motor... That is, once he knows for sure that his motor is tuned properly with the new EFI setup.

I was just answering your question as to why people thought he needs a different cam, I'm not necessarily saying a new cam is going to be the ultimate solution.

 

[Rick James]

He only needs to change the cam if he WANTS a 7000rpm monster,otherwise a efi performer intake and tune should put him at similar power levels as before.If he thinks slapping a victor efi intake alone is gonna make it pull to 7000rpm alone,its not.In that case he should get a cam.He has to match the parts correctly.If he wants to use that intake=needs cam,wants to use that cam =needs intake.

 

[90lxcoupe]

that victor intake is overkill for those heads, i would think about the RPM II if thats an option. The RPM II is an excellent all around intake. also, ive heard that a carb'd motor will tend to make more peak power than an EFI motor will, and the EFI motor will make more TQ then the carb'd motor... which makes perfect sense to me in this situation. You are down 20 HP but you looked over the face that you are up 20 ft lbs of tq

from the sounds of it you went to a pretty half assed shop if you didnt get a wideband, and one pass is going to tell you absolutly nothing. If it was me i'd find a shop that knows what they are doing, and not go back to the dyno without a adjustable regulator also

i wouldnt worry about the distributor, the stock pieces generally work pretty well and you've got a pretty mild combo there.

EDIT: I just read about the rpms not working on the dyno... so how do you know that the information on the dyno sheet is actually correct? stock tachs are know for being very unreliable and for all you know the dyno could have been off by 500 rpms. If that was the case then mabye you were actually making peak tq at 6k not 5500

 

[Bullitt]

Thanks for the responses! As far as some answers due:

Intake selection: picked the Victor EFI based on using Engine Analyzer 3.0 software to simulate the engine. I was able to model the Carb setup fairly accurately against the actual dyno results so my assumption was that with an accurate intake model (runner size and length) that it would at least give a reasonable assumption of performance. Also restricted as I have the tall Ford valve covers which won't allow me to run lots of intakes (for instance the Holley Systemax II I bought doesn't fit even with a spacer). I don't know if a Performer RPM II will fit the tall valve covers, anyone have guidance on this?

Car is a street car, but it's got 3.73 gears and it's a weekend car. It occasionally sees autocross duty in which I try to stay in 2nd gear and like being able to hit at least 65MPH before having to shift, hence the bias towards a little higher RPM.

As far as RPM not working on the dyno, that correct. The RPM and torque curves are calculated. I back calculated from the dyno wheel speed using tire diameter, gear ratios, etc. There is probably a little error here, but not much.

What are people's experience as far as dyno results with similar setups and a "milder" EFI intake and a 306? I realize I'm giving up a little torque with the Victor, but if it'll pull to 7, I'm happy. I don't have much of a gauge to see if the #s are ballpark or not...

 

[Rick James]

I wouldnt spin the engine to 7000rpm too often,unless your confident the valvetrain and bottom end can handle it.Best bet is to go to a real dyno and work with what you have,see what the dyno reveals and go from there.I hope the shop that did your last dyno didnt charge you.

 

[Bullitt]

Going to go to another shop and give an adjustable regulator a shot. It's got a good bottom end (DSS built / balanced) with a windage tray, Fluidamper balancer and upgraded valvetrain parts, so I'm not too concerned with the occasional trip to 6500 or more.

Only reason I got it dynoed without a tune was to help out some other guys that needed a spot filled in a dyno day. Only $40 and helped out some friends so not that worried on that front.

Thanks again for the input.

 

[90lxcoupe]

the rpm II will definitly fit with a tall cover, i had the same setup before, i would get rid of that intake... and you might want to watch valve float spinning the motor that high, my valvetrain is pretty stout on my car and i hit float at about 6800.

also, there are alot of variables with dynos, the air plays a big part in how much power is displayed, and even the way the car is strapped can affect the readout. no two dynos read the same

 

[Bullitt]

Thanks again for the input. May keep a sharp eye on ebay to see if a Performer RPM II pops up. Going to make a trip back to the dyno soon and do some tuning and see what I can get out of it.