Modman Maniac!

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Rat Patrol

Rat Patrol

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B4 I get to the guts of it - I should say that I m a very practiced tuner of Edelbrock/Carter carbs ..and Holleys don't present much of an issue when tuning for WOT HP.

I say this is because this post is not a cry for help- its simply about the cycle of tuning I've been going through wit this intake and what I've found.

So,

As some would know - I experienced a persistent Lean bog issue running my 800 cm Eddy Thunder at the track, although the 112 mph the car ran was pretty good considering what I know now.

Drilling the pump shooter revealed where the problem was...but didn't fix it completely so I bought a ProSystems 830cfm Holley from a mate.

The double pumper fixed the issue - improved my 60ft by a tenth but the car was slow out of the hole and my half track MPH went DOWN and my final MPH dropped back to 110mph.



So Pause for thought - spoke with Patrick from ProSystems who was surprised the car ran as well as it did - He believed the carb was simply too big.

So I asked around and sure enough - most who have used this intake with one carb have had similar issues - and one guy even put a temp gun on the outer pipes and determined that all four outer cylinders ran very lean using one carb on this intake.

Then someone sent me this - which is Indy's own admission that the intake is designed for multiple carburetion.

http://www.moparmusclemagazine.com/...pp_1209_late_model_hemi_intake_mod_man_mania/


So that was enough for me - and here's where I am at in my latest endeavours to prove running a carb or two on these motors is not as insane as it sounds....






 
I hope you get back to the MPH you were at or better. I dont see how with the right tuning your combo cant be at 115mph actually.
 
Keep us posted! That looks sweet, you on a go back to Carter's? Or holleys?
 
Very nice Rat!! I like the air cleaner!!
 
Thx JoeJr - trouble is the base was designed for the early small neck Carters...so I spent two nights grinding the holes out, cutting the centres out of a couple of bases and using MT screws and epoxy to secure them in the holes....

 
Well...I got the dual quad Eddies fitted and I can already tell it has much more mid range than previously - and this is b4 Ive done any fine tuning on the dyno.

Im amazed at how much more part throttle torque the motor seems to produce.

No HP figures or ETSs to quote yet...hope to get the car on the chassis dyno on Monday...




 
Thx Jason - I'll make sure I post comparison dyno sheets - same chassis dyno as last time - and in my experience its pretty accurate going on track results....
 
On the dyno -

IMG_0493_zps0fc307e1.jpg


IMG_0494_zps966b0f75.jpg
 
results -

No ambient temp or intake temp sender corrections used - tested on a 72 deg day. So it is what it is.

Also - this chassis dyno is pretty accurate for my car - Ive verified RWHP plus losses vs my track mph/ weight and it came in within 10fwhp!!

(PS if you're brave..next time you run on a chassis dyno..tell the operator to disconnect the air intake temp sender...you'll get a REAL rwhp reading with no silly corrections)

1st graph shows peak RWHP at 13.8 AF - previously the motor has shown peak HP at 12.69..so there may be a little more in it.


Drivetrain losses are easily 20% - thru 727 torqueflite auto, 3800 stall and 8.75 diff - so I make it around 450HP at the crank.


photo_zps555fea30.jpg



Second graph is comparison between single carb and dual carbs - no other changes - appx 30 RWHP difference ..or appx 45 Crank HP.

Thing I'm most impressed with is the torque increase....


IMG_0495_zpsbaa4b660.jpg
 
Very nice graph, really glad you included the before and after.

It is abundantly clear that anyone choosing to use the modman intake should run dual quads if running carbs.

Now we need to know if it cured your off idle stumble.

Keep the posts coming.

Regards,

Joe Dokes
 
fantastic. There should be a law to show the modifications and changes and the results approved on a Dyno. Thank you. Maybe more or less the numbers are good for a XV intake with a 750 Holley?
 
No Buschi - the figures on the right axis are "tractive effort" - fairly irrelevant.

My limiter is set to 6800 rpm...but it was still making power when it hit the limiter.

Above 6800 you need good valve springs and extra oil capacity.

Not sure how the XV would go with a Holley....I would say a Holley 750 DP would be close the the ideal single carb for these motors - using a " normal" intake like the XV.
 
ah, ok. No, I didn't read the bar on the side. I counted the squares... ;) I made already experiences with the valve springs and those dampers. I have a new set in. Better quality. But I'm a little afraid to rev that high again so I set my limiter at 6500. :)
 
looking again at the MAP curve. Wouldn't it be good for a street car to have similar to distributors a vacuum at idle of zero and increasing to your 12 at maybe 1200 rpm ?
 
Distributors with vac advance are experiencing vacuum at idle. Thats why we disconnect the vac advance before setting mechanical timing at idle.

With the Msd we use MANIFOLD PRESSURE (MAP) not vacuum - so at idle there is always LOW MAP (high vac).

Having MAP advance available at idle manifold pressure aids in having an efficient idle - just as it does with a vac distributor set up.

Is this what yoy're asking?
 
Rat Patrol, I was disappointed at the start of your build you announced you were going with carb instead of the stock manifold and EFI. So now, I don't know what difference there is between the dynos, transmission efficiencies, etc., but when a bunch of buddies with new Challengers all had their cars dyno'd, the 6.1 SRT8 cars were putting out over 380 rwhp. The 5.7 Eagle R/Ts like mine were putting out around 335 rwhp. These were stock to very mildly modified cars (CAIs, aftermarket cat-back, etc.) You really ought to reconsider putting your 6.1 intake and EFI back on. (?)
 
Sorry for the long rant - but some may find this informative..........

This argument of excessive Rear Wheel HP arises often - especially on the LX Forums - but there's a simple way to resolve it -

First - parasitic losses. They are all different, but I've discussed this enough with US dyno operators to know that you will lose an absolute MINIMUM of 17% though the drivetrain on an LC/LX car.

Big wheels and sludgy auto make 17% a very generous figure - in reality its more like 20% - but lets stay at 17% to illustrate my point. :)

The "math" - We take the "380" RWHP recorded on these various RW Dynos and add the 17 % parasitic losses of the drivetrain - The formula is 380/ .83 = 457.83 Engine HP.

(IF we had used 20% - it would be 380/.80 = 475 Engine HP!)

So...................

............. the first question that has to be answered is - Do you think these "380" RWHP cars are actually making 457 Fly wheel from the factory?

Answer - those with a tune and cold air MAY be - those with no mods definitely ain't - Why?

Because stock track MPH vs weight posted on various forums shows they are nowhere near it.


Or....

Lets work backwards - take the FACTORY output of 425 Engine HP - take 17%. losses....Hell..lets take 15%..which is unheard of in auto trans cars..... the result is losses of 63 HP...= 362 RWHP..... So how is a factory 6.1 making 380 rwhp???????

The Rear Wheel output figs I have read on LX Forums for a 6.1 vary from 350 to 390!! ..so the argument that the factory rating is "under-rated" just doesn't hold water.


The problem - The issue lies with Rear wheel dynos - pure and simple. They are a tuning tool - unless the results can be calibrated against track performance...(More on that later)


Then - I would also ask your friends Dyno operators if the Dyno intake temp sensor was used..this "convenient" device is supposed to compensate for excessive high or low engine bay temps - trouble is..its usually far to generous and not a realistic compensation -

I always leave it off - after all, no one changes the weather at the track for me ;)

Then I would want to know - What type of chassis dyno, and there are other factors as well - Ambient barometric conditions are also "conditioned" by the dyno to achieve the final output figure. The SAE conversion factor varies from country to country as well.

Also - What tyre pressures? I made 25 RWHP once by pumping my tyres 15 psi more.

And then - Do dyno operators want return business? Its usually in their interest to make sure their livelihood is "protected"..so a "happy" dyno is a "happy" customer.


Here's a story..........My car made 366 rwhp on another chassis dyno with a single carb - But I knew that was bs from what the car ran at the track.

...then another Dyno said 310 rwhp.

At the time my car weighed 3650 and ran 111 mph - most calculators put that at appx 400 engine HP.......Guess which dyno I believe?..Certainly not the one that said 366 rear wheel!!


The simple truth is - you can't race RW dynos. They vary so much...and so much is at the discretion of the operator and the type of dyno.

Unless you reference them against weight and track MPH and add REALISTIC losses (like I have)....they can say anything....usually on the + side.


I don't doubt several of your friends recorded higher numbers than mine - but tell me what MPH they ran at the track - and I'll tell you what the REAL HP output is of their motors....give or take 10 HP.


Finally! - MY HP rating is probably down a little compared with the = EFI motor....but its not losing a huge amount...and I haven't run the AF anywhere near as rich as it should be....so there's more in it.

Anyhow..track time will tell ;)



PS - Here's a prediction - if my car is making a genuine 450 at the crank - it SHOULD run around 114mph for its weight....I'll be sure to post back and go thru the results. :)
 
its ok that way. I'm al little used to european carbs with idle screws. The throttle is closed and no vacuum at the port. Vacuum comes as soon as you touch the throttle on the port.

Different story. Yep, I mixed the MAP signal up with vacuum numbers. :) It is the other way round. High MAP, low Vacuum
 
Cuda SRT8 said:
Rat Patrol, I was disappointed at the start of your build you announced you were going with carb instead of the stock manifold and EFI. So now, I don't know what difference there is between the dynos, transmission efficiencies, etc., but when a bunch of buddies with new Challengers all had their cars dyno'd, the 6.1 SRT8 cars were putting out over 380 rwhp. The 5.7 Eagle R/Ts like mine were putting out around 335 rwhp. These were stock to very mildly modified cars (CAIs, aftermarket cat-back, etc.) You really ought to reconsider putting your 6.1 intake and EFI back on. (?)
Click to expand...

Well Im nothing if not a man of my word - and I have to say that at this time, the Modman is an under- performer compared to = spec EFI cars.

Here's my latest findings:

With dual quads chassis dyno tuned and with further fine tuning at the track, the car ran 113.2 mph at 12.2.

The UP side -1. This was 2.5mph and .27 tenths faster than my best run with a single carb.

Track conditions were average- cold air but high humidity.

The DOWN side -

1 - The off idle launch is still horribly lean - resulting in a 1.9 60ft. This was re-enforced by some post track tuning where I drilled the shooter on #2 carb and it has already shown significantly more torque at launch.

2 - The mph is still down on = EFI SRT MAX cammed cars and comparing mph/ weight shows a deficiency of about 40 crank HP ..Maybe even a little more....mine coming in around 430 fwhp on the Wallace, Stealth and Moroso calculators.


So where to from here?

The poor 60ft indicates that the fuel distribution is still an isssue with this intake - both air speed and AF need more attention so I plan on trying a couple of Brodix turtles to enhance bottom end torque even more and swallow up some plenum volume.

Im also hopeful that better distribution will benefit my top end...and along with better air I may yet see my target 115mph

If I can get the 60ft down to 1.75 and my mph up to 115 - the car will be making a genuine 460 hp and Ill be satisfied . It will still be down a little on similar EFI cars but I can live with that - I just lift the hood:finga:

Hopefully by the end of this - people will be able to consider the Modman with modifications as a viable dual carb alternative where carb induction is required and folks want to avoid running a scoop.
 
From what I hear about that intake for the LA small block is it is effective on very large 420+ Ci and more importantly high rpm stall, and hi rpm redline, like 7k minimum. Definitely dual carb or six pack setup. Not many running this animal. Good luck.
 
EL5DEMON340 said:
From what I hear about that intake for the LA small block is it is effective on very large 420+ Ci and more importantly high rpm stall, and hi rpm redline, like 7k minimum. Definitely dual carb or six pack setup. Not many running this animal. Good luck.
Click to expand...

Yeah...the issues confronted are very similar to the old tunnel ram problems back in " the day". - either extreme gears and converter or big cubes or modifications are needed.
 
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