Streetable Eight Stack

[Terry Oxandale]

Hi all,

I have put a lot of effort into setting up and fine tuning a Speedmaster budget 8 stack for the street on a cammed LS3. It runs pretty good. There are a few things relevant to this discussion.

- IR intakes do not produce a MAP signal that is properly representative of engine load unless they have a large common plenum, so normal speed density tuning does not work very well. Fueling as a function of throttle position is the standard approach with IR intakes - usually referred to as Alpha-N fueling.

- The fueling requirements change significantly for very small changes in throttle position from idle through to cruise, so they are fussy to tune down low, the fuel table requires heaps of resolution for the first 10% or so of throttle opening, and it's not feasible for this part of the fuel table to be self learning in my experience.

- Linkage quality and precise set-up is really important. I had to throw away or modify this area of the Speedmaster set-up, whereas the Hilborn EFI on my race car is excellent in build-quality and close tolerances by comparison. I think the Hilborn will be great on the street if you physically set it properly.

- If you run Hilborn, you might be best to use dual WBO2s (one in each bank) or one WBO2 that can see both banks (like in an "X" pipe) for closed loop mixture control in cruise conditions that use the whole engine average, because the Hilborn butterflies open in different directions bank to bank with reference to the port and injector position due to the cross-link vs capstan linkage. I don't think that's a biggie though.

In summary, in going the IR route on a healthy engine, you are signing up for an extensive tuning and set-up process, but the results will be excellent if you get it right. It is unlikely you'll get there sticking with speed density tuning and auto-learning using a wizard style approach.

Cheers, Andrew

Andrew, based on my experience (homebuilt IR/ITB setup using the Holley self-learn, I would push back at least on the initial bullet point. I run speed density on mine (48mm) with highly progressive throttle geometry, and find it VERY streetable, and obviously trackable. Currently using a stage 2 Livernoise cam, so it's not close to stock, has a little chop, and works great. Throttle response is excellent. This LS1 has 554 HP/517 ft/lbs. The tuner guys thought I was making a big mistake not going to alpha-N, but once it was on the dyno for tuning, they changed their minds. I do run eight vacuum signals (one from each runner) to a common plenum (the bellcrank mounting column) for the vacuum signal, with TPS, temp, WBO2, and RPM being other inputs. Works very well. I personally feel that any ITB set-up will always have personal modifications that must be made to them to make any of them work perfect. "Bolt-on" is a myth to me, but I'm sure the VERY expensive ones are not. I am currently repeating this project with a new LS3 using a rectangular port intake (bored LS3). BTW, thanks for your great insight and post!

 

[Andrew Robertson]

Andrew, based on my experience (homebuilt IR/ITB setup using the Holley self-learn, I would push back at least on the initial bullet point. I run speed density on mine (48mm) with highly progressive throttle geometry, and find it VERY streetable, and obviously trackable. Currently using a stage 2 Livernoise cam, so it's not close to stock, has a little chop, and works great.

Hi Ox, I love your fabricated IR solutions!

I run speed density on the Hilborn 440SBC in the canam car and it is super docile and well mannered so i agree with you there. The issue it has got though is that the MAP resolution is poor due to the IR so in the lower to mid RPM range it will supply pretty much the same fuel at say 20% TPS that it supplies at 100% TPS - this means it is very fat at medium load even though I have got it good wide open and at idle. That's no problem on a race car but I am chasing decent levels of economy on the other IR set-up in the road car. Do you have that issue or have you solved it with closed loop fuel trim?

Keep us posted on the new build!

Cheers, Andrew

 

[Brian]

Wow Terry. If I think I'm seeing what my eyes are telling me, well done.

I want to share the virtues of the MS2 hybrid set up. I have a similar situation with the single plenum to get a MAP signal, but the nice thing about the MS2 hybrid is when the MAP drops below 85% of atmospheric pressure, it goes to an alpha N fuel map. Once your're to 85%, MAP doesn't matter. It's almost WOT, and that's the easiest part to tune.

Interesting thing, at 1200 RPM, 15% throttle will drop MAP to 90%. but at 4500 rpm, 50% throttle is close to 50% load. So that 85% map change moves with RPM. It makes the hybrid map both very driveable and actually fuel efficient.

 

[Andrew Robertson]

I want to share the virtues of the MS2 hybrid set up. I have a similar situation with the single plenum to get a MAP signal, but the nice thing about the MS2 hybrid is when the MAP drops below 85% of atmospheric pressure, it goes to an alpha N fuel map. Once your're to 85%, MAP doesn't matter. It's almost WOT, and that's the easiest part to tune.

Interesting thing, at 1200 RPM, 15% throttle will drop MAP to 90%. but at 4500 rpm, 50% throttle is close to 50% load. So that 85% map change moves with RPM. It makes the hybrid map both very driveable and actually fuel efficient.

Very useful sounding feature indeed

 

[Howard Jones]

So this kind of question always gets me wondering what is available IF I wanted to do this myself. The first post was based on the investigation I did about 7 years ago when I was interested in using an EFI on my SLC SBC track motor instead of a Holley 4 barrel. I called several of the different EFI manufacturers I could find and the Holley backroom tech guys were the most helpful. That was the discussion about fuel maps. individual port injectors and manifold vacuum came from.

These guys impressed me then but I couldn't justify the cost. They were very interested in my cam specs as well as the overall use of the car. At the time I was going to use a 4-barrel throttle body not an 8 stack but otherwise I liked what I heard, I just couldn't see spending $6-7K more than a carb and arrive at near the same HP. They are closer to $10K now,

JIM INGLESE 8-STACK SYSTEMS

jiminglese.com

 

[Glenn M]

A point I like about the Weber look EFI v actual Webers, having run both, is that the carbs have to be choked down to work properly (on the road anyway) so your 48mm could actually be 10mm less, whereas the EFI doesn't need this, so WOT sees the full fat 48mm bore.
I did a speed run at an RAF airbase and was radar clocked at 187mph with Webers. I did one after I had changed to the Borla 8 stack with Accel EFI and clocked 192 mph. The general running and fuel economy was vastly better as well. Just adding my tuppence worth.

 

[Randy Folsom]

So this kind of question always gets me wondering what is available IF I wanted to do this myself. The first post was based on the investigation I did about 7 years ago when I was interested in using an EFI on my SLC SBC track motor instead of a Holley 4 barrel. I called several of the different EFI manufacturers I could find and the Holley backroom tech guys were the most helpful. That was the discussion about fuel maps. individual port injectors and manifold vacuum came from.

These guys impressed me then but I couldn't justify the cost. They were very interested in my cam specs as well as the overall use of the car. At the time I was going to use a 4-barrel throttle body not an 8 stack but otherwise I liked what I heard, I just couldn't see spending $6-7K more than a carb and arrive at near the same HP. They are closer to $10K now,

JIM INGLESE 8-STACK SYSTEMS

jiminglese.com

Totally agree, if HP is the goal, then an 8 stack is probably not the way to go, and the same goes for street manners. Especially when it comes to the price. But an EFI 8 stack beats every alternative when it comes to the cool factor . Looking through the back glass of a GT40 and seeing 8 shiny velocity stacks is as master card would say ‘priceless’.

 

[Neil]

Totally agree, if HP is the goal, then an 8 stack is probably not the way to go, and the same goes for street manners. Especially when it comes to the price. But an EFI 8 stack beats every alternative when it comes to the cool factor . Looking through the back glass of a GT40 and seeing 8 shiny velocity stacks is as master card would say ‘priceless’.

"...an EFI 8 stack beats every alternative when it comes to the cool factor ." But if you want to be even cooler than Steve McQueen, put on an eight-stack mechanical fuel injection manifold.

 

[Randy Folsom]

"...an EFI 8 stack beats every alternative when it comes to the cool factor ." But if you want to be even cooler than Steve McQueen, put on an eight-stack mechanical fuel injection manifold.

 

[Ryan L]

01-06 BMW E46 M3 S54 Z4M Individual Throttle Bodies ITB Intake | eBay

<p>01-06 BMW E46 M3 S54 Z4M Individual Throttle Bodies ITB Set 3.2L Intake with rails</p><br /><p>No injectors</p>

www.ebay.com

these are bmw itb's of an e46 m3.

note what looks like 2 fuel rails. the upper one is actually a vacuum tube to link all 6 cylinders together. This is how Bmw did it in a production engine circa 2000s.
I know some of the 8 stack manifolds are linked under the valley cover.

 

[Brian]

I remember reading that type BMW was speed density too.

With larger enough ports and central chamber, at low throttle opening, the engine behaves like a common plenum and the throttle syncing becomes less critical.

 

[Walter]

I have a 302/363 from Prestige Motors that is going into an RCR40 (GT40 replica). It currently has a 750 CFM Quick Fuel carb. I would really like to have an eight stack. I am hoping for guidance. The car will be used on the street and maybe track days once or twice a year.

I have heard that Speedmasters are available from some sources where they fix all the issues and pre-tune the system and as such work fairly well at about half the cost of Borlas.

The engine dynoed at 533 HP which is way more than I need so if I had to give up a few ponies to make an eight stack streetable, that would be fine.

363 Ford Small Block Stroker Crate Engine: F363-SS-C2

Find all the details on our Ford Small Block F363-SS-C2 engine here. Prestige Motorsports in Concord, NC.

www.prestigemoto.com

Kinsler...

 

[Randy Folsom]

Kinsler...

Kinsler certainly has race wins. They don't list prices on their website, which probably means expensive.

 

[Ryan L]

I remember reading that type BMW was speed density too.

With larger enough ports and central chamber, at low throttle opening, the engine behaves like a common plenum and the throttle syncing becomes less critical.

They used a similar set up in the later S65 & S85 engines. The S65 V8 looks to have a plastic manifold in place of the metal pipe. I have not looked for pictures of the S85 V10. not sure on the E46 tuning I know they talk about Alpha N when the CSL airbox is added. in terms of engine size, the 3.2L six has cylinder capacities the same as a 4.2L V8. it is also a long stroke engine with an 8000+ RPM if that makes a difference to the intake velocity fluctuations.

After that they went turbo and I think went to valve-tronic which is an infinitely variable valve lift system that does away with the throttle altogether.

 

[Brian Kissel]

Randy. Pretty much everything Kinsler sells is custom for your application, so no two units are exactly alike. Unlike most companies that sell a unit off the shelf Kinsler requires you to fill out build sheets about your engine so the can build your unit from the ground up. Once they have this information, they run it through engine simulation software. This allows them to determine the correct throttle bore and stack length. I have ordered two different sets of stacks so Prestige can do dyno runs and see how close the simulation software is to the actual dyno run. My simulation shows a big drop in torque at a short amount of rpm width. Brad at Kinslers thought staggered stacks will flatten that area out, so it’s worth a try. At the end of the the day, you can’t race your dyno either. Once it is in the car, I will have it tuned on a chassis dyno.
Below you can see the initial forms and then the simulation information.

Brad at Kinslers is very knowledgeable and willing to help.
Regards Brian

 

[Randy Folsom]

Randy. Pretty much everything Kinsler sells is custom for your application, so no two units are exactly alike. Unlike most companies that sell a unit off the shelf Kinsler requires you to fill out build sheets about your engine so the can build your unit from the ground up. Once they have this information, they run it through engine simulation software. This allows them to determine the correct throttle bore and stack length. I have ordered two different sets of stacks so Prestige can do dyno runs and see how close the simulation software is to the actual dyno run. My simulation shows a big drop in torque at a short amount of rpm width. Brad at Kinslers thought staggered stacks will flatten that area out, so it’s worth a try. At the end of the the day, you can’t race your dyno either. Once it is in the car, I will have it tuned on a chassis dyno.
Below you can see the initial forms and then the simulation information.

Brad at Kinslers is very knowledgeable and willing to help.
Regards Brian

Brian, Thx much for sharing that information. How do Kinslers’ prices compare to Prestige’s? Ryan at Prestige said that because the engine they built for me is popular, they have already figured out the tune with Borla and can just send me the parts to install myself. Of course, like you mentioned, a chassis dyno tune is still needed for optimum performance. Ryan said about $8,500 for complete setup unpolished. Not sure if that included a new distributor, but I think so.

I have heard that a common issue with NA ITB setups like Webers is an RPM drop somewhere between 2,800 and 3,000 RPM. The folks that were racing them back in the day didn’t care because they were running between 5,000 and 6,500 RPM.

 

[Brian Kissel]

Randy, I'm not going to post prices here, but the Kinsler was quite a bit more than the Hilborn unit I originally wanted. Prestige was the one that recommended I upgrade to the Kinsler. The Kinsler does not come with any ignition, or even injectors in my case. Doug at Prestige worked closely with Brad at Kinslers to come up with the proper setup. They offer many options that you can choose from. Hopefully I will get pictures of it before it is shipped to Prestige. If that happens, I will post here.

Regards Brian

 

[Dave Hood]

Prestige installed the Borla Eight Stack injection on my engine a few years ago. Along with Holley Terminator-X EFI. Works really well.

 

[Randy Folsom]

Prestige installed the Borla Eight Stack injection on my engine a few years ago. Along with Holley Terminator-X EFI. Works really well.
View attachment 137987

Dave, that looks so good.

 

[Randy Folsom]

So now I am wondering if Borla's 8-Stack or Throttle Body solution is more suited to my wants (I clearly don't have a 'need'). The 8-Stack definitely looks more period correct. What are the pros and cons of each? My guess is that the 8-stack costs more, but when tuned properly, both systems function about the same.