Streetable Eight Stack

[Randy Folsom]

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.

Performance Engine Builders - Prestige Motorsports - Concord NC

Prestige Motorsports delivers power, precision, and reliability on land and water. Custom engines, turnkey packages, and performance solutions for cars and boats.

www.prestigemoto.com

 

[Brian Kissel]

Search Prestige’s videos where they explain the problems with cheap injection units vs quality ones.

Regards Brian

 

[Randy Folsom]

Search Prestige’s videos where they explain the problems with cheap injection units vs quality ones.

Regards Brian

Found this which is not at all surprising. Basically the knock offs need a lot of work to make them functional.

But, like I mentioned, I heard there are some sources that machine the manifold, fix a lot of the quality issues, etc. Hoping someone can share their experiences.

 

[Howard Jones]

The first thing you need to do is measure your intake vacuum at idle. Once you have this number you can talk to the various FI manufacturers. This will be the first question they will ask you. If they don't then you need to ask to talk to a technical person and not a salesperson.

ALL the self-learning systems require near-stock cam timing (a lot of idle vacuum) to work. Anything with a more aggressive cam (very low intake vacuum, less than 10-11 hg ) will need a port injection system and a "fuel map" type system. As a general rule, the self-learning FI systems will need near-stock vac values of about 16-20 Inches of mercury, in/hg. Much less than about 12-14 in/hg and they will not work or not work well.

Why? Because the self-learning systems use the varying intake manifold vac value to calculate fuel delivery. Stock cams will have about 14-18 in/hg of variation whereas a radical cam can have as little as 5-8. The FI system thinks the engine is always at or near full throttle with a big cam and tends to run too rich all the time.

Here is a discussion on cam timing and vac including various cam specs and associated vacuum figures. You might be able to derive what range your cam might be in from it. As a reference, my first 355SBC had a .480 lift and 290-degree duration cam in it with 10.5 CR. It made 7 in/hg at idle. When I called Holley and talked to an FI engineer he basically said "No way a self-learning system will ever work. You need a system like we use on NASCAR with a programmable fuel map and individual port injection".

List your cam and vacuum specs here. - CorvetteForum - Chevrolet Corvette Forum Discussion

C3 Tech/Performance - List your cam and vacuum specs here. - What are the specs on your cam and how much vacuum do you run at what idle speed? List your experience (likes and dislikes) and what mods (Like a high stall converter) you had to do to make it work right ON THE STREET. Just curious. It...

www.corvetteforum.com

 

[Randy Folsom]

The first thing you need to do is measure your intake vacuum at idle. Once you have this number you can talk to the various FI manufacturers. This will be the first question they will ask you. If they don't then you need to ask to talk to a technical person and not a salesperson.

ALL the self-learning systems require near-stock cam timing (a lot of idle vacuum) to work. Anything with a more aggressive cam (very low intake vacuum, less than 10-11 hg ) will need a port injection system and a "fuel map" type system. As a general rule, the self-learning FI systems will need near-stock vac values of about 16-20 Inches of mercury, in/hg. Much less than about 12-14 in/hg and they will not work or not work well.

Why? Because the self-learning systems use the varying intake manifold vac value to calculate fuel delivery. Stock cams will have about 14-18 in/hg of variation whereas a radical cam can have as little as 5-8. The FI system thinks the engine is always at or near full throttle with a big cam and tends to run too rich all the time.

Here is a discussion on cam timing and vac including various cam specs and associated vacuum figures. You might be able to derive what range your cam might be in from it. As a reference, my first 355SBC had a .480 lift and 290-degree duration cam in it with 10.5 CR. It made 7 in/hg at idle. When I called Holley and talked to an FI engineer he basically said "No way a self-learning system will ever work. You need a system like we use on NASCAR with a programmable fuel map and individual port injection".

List your cam and vacuum specs here. - CorvetteForum - Chevrolet Corvette Forum Discussion

C3 Tech/Performance - List your cam and vacuum specs here. - What are the specs on your cam and how much vacuum do you run at what idle speed? List your experience (likes and dislikes) and what mods (Like a high stall converter) you had to do to make it work right ON THE STREET. Just curious. It...

www.corvetteforum.com

As always, your knowledge is amazing. Prestige said they speced the engine such that it would support an eight stack so my cam is supposed to be compatible. Not sure it is possible for a cam to be compatible with a NA four barrel and an EFI eight stack. I can’t measure the vacuum yet because the engine is still in the crate. The good news is that RCR said my GT40 will be ready to ship in about two weeks. So I might have a home for the engine in a month or so.

 

[Brian Kissel]

I am having Prestige build a Aluminum Brodix BBC for me. I was going to run a Hilborn EFI, and they recommended a Kinsler EFI. One of the things I have read is thermal expansion rates effect the throttle linkage. Hoping that the engine being all aluminum things will expand somewhat the same. I have read a lot about this problem. Time will tell I guess.

Regards Brian

 

[Andrew Robertson]

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

 

[Brian Kissel]

Well said Andrew.

Regards Brian

 

[Paul Proefrock]

Randy
I am starting in on my 5th ITB setup and think I've finally learned enough that I don't get the jitters when I go to start it up. Some points that may help:

• Remember, you get exactly what you pay for. There is a reason for the dollar difference between SpeedMaster and Borla. ITB's are extremely sensitive and totally unforgiving of any slop or tolerance. To run smooth, everything MUST be perfect. even with the Borla systems - it's just easier to get there with them.
• ITB's react differently than port injection/common throttle body. Many comments come from those with only experience with the common throttlebody. I don't dispute their expertise, but ITB's ARE DIFFERENT. If someone suggests using speed density with your setup, run as fast as you can.
• Learn about Alpha-N with MAP compensation. Borla's come with a common vacuum chamber. There isn't enough vacuum to tune via Speed Density but there is enough to fine tune your setup. I'm running a 468" FE with a Borla system. It produces 600hp easily yet will idle at 800 and will get 17mpg. It can be done, just takes a lot of tweaking and not short-cutting on the materials.
• Forget any idea of 'self-tuning' Most ECUs will self-tune your fuel table once you get it set up and running, but it won't address cold start, hot start, accel and/or decel compensation or idle settings. And you need to have all these fine tuned before the 'self-tuning' can become an ally.
• If you are not proficient with electronic fuel injection, anticipate a learning curve that is almost a perpendicular line. You do make a little headway as you are learning about it but it must all come together at the same time to make it work. There are a number of different educational/forums that can assist you.
• The ECU is as important as the hardware. It must be at the higher end of capabilities. Don't try to cheap out, you'll just make your life difficult. Some will tell you the FAST EZ will do it, but it won't. Only the higher end units offer all the settings you are going to need to make the system hum
• When driving my cars, for the most part, you are only using the first 20% of the throttle movement. Yet that flows enough air to run well over 100mph. The difference in airflow between 50% and 100% throttle is minimal. Throttle use/fuel table is NOT linear, you need a lot of resolution at the lower openings. And that's where the linkage needs to be 100% accurate.

Yes, you can take a SpeedMaster setup, a cheap or homemade ECU and a back country road to get a system to run. But will you be happy with it? and will you be able to accomplish that within a given amount of time and money. Study your project well before jumping into the deep end.

But with all that said, you'll really enjoy a finely tuned system once you have it up and running. It's fun to just reach down and turn the key and hear the motor spring to life, without even touching the throttle or being in the seat.

Paul

 

[Julian]

I am having Prestige build a Aluminum Brodix BBC for me. I was going to run a Hilborn EFI, and they recommended a Kinsler EFI. One of the things I have read is thermal expansion rates effect the throttle linkage. Hoping that the engine being all aluminum things will expand somewhat the same. I have read a lot about this problem. Time will tell I guess.

Regards Brian

If the ITB's are bolted to a manifold with center pull throttle linkage you should be okay, I have had issues with a three piece manifold design and idle creep once hot.

 

[Brian Kissel]

Thanks for that Julian. I do have a Kinsler that the ITB’s are bolted on, but this one does not. The picture below is a close representation of what I have coming.
Thank You !!
Regards Brian

 

[Brian]

Not sure how the other EFI systems handle it, but Megasquirt 2 extra has a hybrid alphN/SD algorithm that uses speed density up to about 85% load then switches to speed density.

I heavily modified a speedmaster cheapy 8 stack on a 383 SBC and had it running really well. I had 2 plenums under the manifold in the cam valley with tubing piped into each runner. A large 3/8" tube for a ford 1 wire idle air motor and one with a small 1/4" tube for a vacuum signal.

I've posted it before, but don't have the pics on this computer to share.

The tuning was pretty easy with the megalog histogram data logger. It includes a program to blend the speed density and alpha N maps and scale to get the target AFR. Looked great and ran great.

 

[George]

I installed a Borla eight stack on my slightly modified 302 four years ago and works like a charm. The only issue was changing the EZ FAST ECU that failed two years ago and replaced it with a Holley Terminator X. I would recommend staying away from a FAST ECU. The Holley ECU is self learning and runs great on my GT40.

 

[JP Verweij]

......... but Megasquirt 2 extra has a hybrid alphN/SD algorithm that uses speed density up to about 85% load then switches to speed density.

With TunerStudio MS (Registered) you even have lots of options including Auto Tune and cold start Auto Tune (WUE Analize) & VE analizer which makes it even more versatile.
Loads of support on the WWW about Megascuirt also.

 

[Brian]

I dug up some pics of my heavily modded speedmaster

I swapped the throttle bodies around so the injectors were in the middle squirting more on the back of the valve, added the 2 plenums because the idle air motor would heavily affect the vacuum reading if the map and IAC were in the same chamber with the restriction of the tubing. This also meant redoing the throttle linkage.

One pic shows the ford idle air motor and oil pump drive. I made a 36-1 wheel and used Dodge neon wasted spark coil packs.

I also parted off the trumpets so I could run a large single air filter.

 

[Bill Kearley]

I'm happy with my Borla and Holly management

 

[Randy Folsom]

Randy
I am starting in on my 5th ITB setup and think I've finally learned enough that I don't get the jitters when I go to start it up. Some points that may help:

• Remember, you get exactly what you pay for. There is a reason for the dollar difference between SpeedMaster and Borla. ITB's are extremely sensitive and totally unforgiving of any slop or tolerance. To run smooth, everything MUST be perfect. even with the Borla systems - it's just easier to get there with them.
• ITB's react differently than port injection/common throttle body. Many comments come from those with only experience with the common throttlebody. I don't dispute their expertise, but ITB's ARE DIFFERENT. If someone suggests using speed density with your setup, run as fast as you can.
• Learn about Alpha-N with MAP compensation. Borla's come with a common vacuum chamber. There isn't enough vacuum to tune via Speed Density but there is enough to fine tune your setup. I'm running a 468" FE with a Borla system. It produces 600hp easily yet will idle at 800 and will get 17mpg. It can be done, just takes a lot of tweaking and not short-cutting on the materials.
• Forget any idea of 'self-tuning' Most ECUs will self-tune your fuel table once you get it set up and running, but it won't address cold start, hot start, accel and/or decel compensation or idle settings. And you need to have all these fine tuned before the 'self-tuning' can become an ally.
• If you are not proficient with electronic fuel injection, anticipate a learning curve that is almost a perpendicular line. You do make a little headway as you are learning about it but it must all come together at the same time to make it work. There are a number of different educational/forums that can assist you.
• The ECU is as important as the hardware. It must be at the higher end of capabilities. Don't try to cheap out, you'll just make your life difficult. Some will tell you the FAST EZ will do it, but it won't. Only the higher end units offer all the settings you are going to need to make the system hum
• When driving my cars, for the most part, you are only using the first 20% of the throttle movement. Yet that flows enough air to run well over 100mph. The difference in airflow between 50% and 100% throttle is minimal. Throttle use/fuel table is NOT linear, you need a lot of resolution at the lower openings. And that's where the linkage needs to be 100% accurate.

Yes, you can take a SpeedMaster setup, a cheap or homemade ECU and a back country road to get a system to run. But will you be happy with it? and will you be able to accomplish that within a given amount of time and money. Study your project well before jumping into the deep end.

But with all that said, you'll really enjoy a finely tuned system once you have it up and running. It's fun to just reach down and turn the key and hear the motor spring to life, without even touching the throttle or being in the seat.

Paul

Paul, I really appreciate all the information you provided. I called Prestige. They tell me the Borla setup they provide is pretty close to optimal tuning as shipped since they have installed it on engines just like mine many times. And they will help with the final tune after I get it installed. It is not cheap, but after reading your’s and other’s comments it seems like it is probably worth the extra $2,500 as compared to a comparable Speedmaster setup.

 

[Randy Folsom]

I'm happy with my Borla and Holly management

Looks awesome

 

[Randy Folsom]

I dug up some pics of my heavily modded speedmaster

I swapped the throttle bodies around so the injectors were in the middle squirting more on the back of the valve, added the 2 plenums because the idle air motor would heavily affect the vacuum reading if the map and IAC were in the same chamber with the restriction of the tubing. This also meant redoing the throttle linkage.

One pic shows the ford idle air motor and oil pump drive. I made a 36-1 wheel and used Dodge neon wasted spark coil packs.

I also parted off the trumpets so I could run a large single air filter.

Thx much for sharing. Very nice setup. I think the expertise to build a system like yours is beyond my capabilities.

 

[Randy Folsom]

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

Thx much for the guidance