Jenvey Heritage EFI

[princeout]

These look really interesting!

Heritage EFI

Anybody try this on a U20?

Tim

[Pjackb]

This look cool
Old school look on a modern engine (SR20) or Hidden EFI for your U/R engine
Would they just work and sound like any ITBs

[fj20spl311]

I and others have used the DCOE/SOLEX replacements from TWM/Borla with some success.

I love the look, but I am concerned they are not available in taper bore or with some sort of venturi.
Don't know if straight ITBs should be sized according to choke or throttle plate of the carburetor.

[fj20spl311]

I found this informative. esp. ITB sizing
up to 46 BHP/cylinder - 38mm,
up to 51 BHP/cylinder - 40mm,

Throttle Body Selection
NOTE: It is assumed that the advanced engine developer will have access to the usual experience / software / dyno time. The advice on this page is not intended to replace these.
Which type of throttle body ?
Twin bodies are the most straightforward solution for production engines, direct-to-head where available, or via a suitable manifold.
Direct-to-head-bodies represent the simplest and neatest solution. They are harder to match to the inlet ports if this is required for the engine in question but have the advantage of being angled for best results, unlike a carburettor manifold.
Single bodies represent the no compromise solution, particularly for competition use. The seperate manifold is easily matched to the inlet ports and the best mixture path is guaranteed. They are also available in fully tapered bore and twin injector types. Mounting, balance and maintenance are naturally more involved.
What is the best throttle body diameter ?
Factors influencing size are; Power output, RPM, cylinder head design, cylinder capacity, position of the throttle body in the inlet tract and position of the injector.
Choice of bore size is a balanced compromise resulting from the following;
1) A larger bore leads to lower flow resistance, but obeying the laws of diminishing returns.
2) A smaller bore leads to better throttle control and response (never underestimate) and improved fuel mixing.
3) The system should be considered in total - from (at least) trumpet flange to cylinder and proportioned accordingly.
Basic references for BHP per cylinder, assuming ca 120mm from butterfly to valve head and a max of 9,000 rpm are;
Up to 30 BHP - 30mm, up to 33BHP - 32mm, up to 39BHP - 35mm, up to 46 BHP - 38mm, up to 51 BHP - 40mm, up to 56 BHP - 42mm
Up to 65 BHP - 45mm, up to 74 BHP - 48mm, up to 80 BHP - 50mm, up to 87 BHP - 52mm, up to 93 BHP - 54mm.
These power figures may be increased by up to 10% in a purpose designed and well proportioned system.
As butterfly to valve distance increases, butterfly size will need to increase in proportion to system taper and vice versa.
Lower revving engines and those with injectors placed before the butterfly will generally accept a larger body.
What is the correct overall system length?
Induction length is one of the most important aspects of fuelling performance engines.
In our experience an under-length system is the greatest cause of disapointment, with loss of up to 1/3 of power potential. There are a number of good books on the subject and the serious developer is referred to these and, in particular, dyno trials. A guide figure, from the face of the trumpet to the centre of the valve head is 350mm for a 9,000 RPM engine. Other RPM are proportional i.e. for 18,000 RPM the figure is approximately 175mm.
Any air feed system to an airbox or filter can have a large effect on the power curve and must be considered carefully particularly if the airbox is small.
The induction system is part of a resonant whole from air inlet or trumpet to exhaust outlet and the ideal length is heavily influenced by the other components.
What is the best position for the butterfly?
The butterfly is an important aid to fuel mixing. When positioned too close to the valve this advantage will be lost whilst positioning far away may lead to a loss of response.
As with the injector position (see below), higher RPM demands a larger butterfly to valve distance. A practical minimum figure for a 7 - 9,000 RPM engine is 200mm, whilst the maximum is dictated by the need to fit an air horn of reasonable length to achieve a good overall tract shape. One solution to this apparent compromise is the use of bodies with fully tapered bores which, in effect, extend the trumpet distance beyond the butterfly and into the manifold. For very high speeds above approximately 15,000 RPM, the ideal butterfly position is only just inside, or even outside the trumpet and a point is reached where a taper is no longer sufficient for good tract shape. For these circumstances we can supply bodies with the exponential trumpet shape machined into them as a special service, or barrel bodies which, by their nature, must be purpose designed in conjunction with the cylinder head.
Where is the best place for the injectors?
Where one injector is to be used per cylinder the best compromise position is immediately downstream of the butterfly. This gains maximum advantage from local turbulence and gives results surprisingly close to the optimum at both ends of the rev-range. This is the recommended position for most applications.
For performance at low RPM, economy and emissions the injector needs to be close to the valve and firing at the back of the valve head. This is the favoured position for production vehicles.
For higher RPM (very approximately 8,000+) the injector needs to be near the intake end of the induction tract to give adequate mixing time and opportunity. The higher the RPM, the further upstream the injector needs to be. As a result, use of speeds above approximately 11,000 RPM may give best results with the injector mounted outside the inlet tract altogether (see our remote injector mounting). It is common to fit both lower and upper injectors in such a system to cover starting and low RPM, as well as high speeds.
What is required for a complete fuel injection system?
Besides throttle bodies, linkage and manifold (if required) typical components are; A management system, wiring loom, fuel pump, fuel pressure regulator, fuel injectors, appropriate plumbing, air horns and a ducting / filtration system for the incoming air.
What type of injector?
Dimensions: All Jenvey injector mountings and fuel rails will accept either the standard 'O' ring mounted injectors for 14mm bores as supplied by Bosch, Weber, Lucas, etc (64mm between 'O' ring centres) or the shorter 'Pico' style injectors (38mm between 'O' ring centres).
There are a number of other injector types, using the same 'O' rings but with different lengths. These can be used on our twin throttle bodies with ease, but may require different fuel rail mountings on individual bodies. Please specify which you are using when ordering throttle bodies and fuel rails.
Flow-rate: When fitting our throttle bodies to an otherwise standard engine bear in mind that increased power means increased fuel demand and the original equipment injectors are therefore usually inadequate.
What manifold to use?
When injecting into the throttle body (e.g. our types TB, TH, TF, TA, direct-to-head and SF, SS or ST//1), most of the mixing occurs within the manifold section. It is therefore important that the manifold is suitably proportioned to evenly accelerate gas speed and thus help fuel mixing and distribution. The straighter the run in to the ports the better. A manifold which curves in the same direction as the valve throats is preferred to one which causes the flow to pass through an "S" bend.
What throttle potentiometers will fit Jenvey bodies ?
We use relatively popular mechanical interfaces for the throttle potentiometer. Popular types are; Colvern CP17 series (as supplied by Jenvey), Wabash 971-0002 and (via fitting kits) throttle pots from Novotechnik, Penny & Giles, Marelli and Weber. A number of production car throttle pots (e.g. Rover K series) will also fit directly to the bodies.
The Colvern CP17 throttle potentiometer may be mounted to either end of most installations and spindle rotation is typically 82o.
Can Jenvey bodies be pressure charged?
Jenvey bodies can generally be used with boosts up to 6 bar, although we recommend that you contact our technical department if boost of more than 2.5 bar or temperatures above 150ºC are expected. Some models require special treatment for high pressures and/or temperatures.
Can Jenvey bodies be connected to an Air Bypass valve?
Components and complete kits are available to connect the output from an ABV to throttle bodies. More information is available on a specific instruction sheet.
What is the best Air horn ( Trumpet / Stack / Bellmouth)?
The air horn serves three main purposes;
1) To convert the pressure difference between bore and entrance into air velocity with the minimum of energy loss.
2) To act as the interface between the induction system and the atmosphere, i.e. the point at which pressure waves change sign and direction.
3) To complete the system to the required overall length.
For ease of description the air horn may be considered in two parts; the 'flare' and the 'tube'.
The main job of the flare is to spread the low pressure zone over the largest possible area, to reduce local pressure reduction, whilst guiding incoming air into the tube with minimum disruption or induced vortices. The flare should be shaped to encourage air to enter from the sides but not from the rear of the mouth. This is achieved by either finishing the mouth with a sharp edge when the arc is a little beyond 90o from the air horn axis or by folding material back, parallel to the axis, when the arc is at, or just below, 90o to the axis.
The main job of the tube is to accelerate the airflow smoothly and progressively. This is best achieved by an exponential shape, i.e. one where the radius of curvature is increasing constantly until the angle of the sides matches the next part of the system, usually the throttle body.
It should be noted that the requirements for fuel injection and carburation do not always coincide and the best horns for one may not suit the other.

[mtresillian]

The Jenvey website has some very good information. I have 45mm ITBs on mine. They are too big. 40mm would be better...and perhaps 38mm if sticking with 2L engine. The throttle response and mid-range pull is solid on a solex I've driven with stock chokes. The 37mm chokes give a little more top end at the expense of torque. Both cars are pretty muvh equal on the road but on winding roads the torque will be your friend. The difference is very noticeable.

[fj20spl311]

I have 45mm ITBs on mine.

Is it possible to put chocks in the intake manifold?

[Pjackb]

Copying a good article on the subject

What size ITB should I use
ITB intakes are the most effective intake for a naturally aspirated engine there is absolutely no question about that and that is why the most powerful racing and performance engines will all have an intake like this in some form or another. However there are a lot of myths and misconceptions about them and their application to an engine. Firstly they are not reserved only for high rpm engines with huge cam duration and extensive head modifications. Secondly if the system is sized correctly they will not cause and engine to loose all its torque and drivability, in fact quite often they can even improve low end torque as well as improving top end on even a stock standard engine. How you might ask? well it all comes down to a combination of two critical aspects: air velocity and runner length. Production engines have to make a lot of compromises to meet various requirements such as production costs, space restrictions, emissions, economy, reliability and tuning stability. All these things make an ITB type intake on production engines something usually only reserved for high performance and sports vehicles where the additional costs can be justified, so for every other engine that leaves the door open to make some improvements. Lets get back to those two critical design aspects I mentioned before, the first is the air velocity this is most critical above everything else. The velocity is directly proportional to the cross section area of the runner, i like to work in equivalent diameter to keep everything clear in my head. So it stands to reason that the smaller the diameter the higher the air velocity for a given cylinder displacement.

WHAT SIZE IS RIGHT?
This is provably the most important question to ask for installing a successful itb system. There are some basic rules to follow and they might be surprising to most people because probably the single biggest mistake most people make is using an itb that is too big. I have to point out here that its the runner size that’s most significant and the ITB should be appropriately matched to the runner both before and after the actual butterfly plate. The ultimate size of the runner is proportional to the total air flow requirement which in turn is linked to the power output of the engine, so by this theory we can use the power level as an indication of the size that is required not the engine displacement. The length of the intake runner at which the power is delivered is related to rpm, but more on that aspect later.

The single biggest mistake most people make is using an ITB that is too big

For any engine to operate at its optimum efficiency it relies on a critical level of air velocity, this creates a ram effect during the induction stroke. If the velocity is too low then there is not enough kinetic energy in the intake charge to achieve a high level of cylinder filling. This will affect the power at all rpm levels, the intake charge cant obtain enough velocity at peak torque rpm to fill the cylinder well so it will be boggy and unresponsive then as rpm rises and the efficiency of the engine falls the cylinder still wont achieve the required velocities to fill the cylinder quickly enough during the valve opening period and the engine will never reach its full potential. On the other hand if the velocity is too high then the engine will make excellent torque and mid range power due to the high velocities but at some stage as the rpm rises the power level will be slightly less than the maximum potential due to flow loss known as choke. Here you should focus on the rpm that the engine will operate in most and remember you need to travel through the mid range to reach the peak. An ideal intake port and runner has a tapered section from the trumpet or bell-mouth and a high velocity section all the way to the bowl area just before the valve, If it were straightened out it would look something like this picture below.

E37CB921-EE06-46E4-8555-35FB5A1DE556.jpeg

The throttle plate can be placed at any location on the intake runner so you can see that the location of the butterfly will largely dictate the size it should be. This is why some extremely high power engines appear to have quite small ITB”s because the placement is closer to the valve, while other engines appear to have overly large ITB”s, for example a BMW m3 engine has 50mm ITB but they also have 2 very long ports in the head that are only equivalent diameter of 37mm this is the high velocity section of the intake and the butterfly is effectively out near the bell-mouth. This is why everyone who adapts M3 ITB”s onto other engines results in a spectacular failure!

As a rule of thump if the flow capacity of the head is known then the ITB should be in the range of 120-140% of the head flow. But this all depends heavily on the assumption that the intake runner/port of the original engine is the optimum size in the first place! many production engines have ports that are already too large. Another way to estimate is by the power output of each cylinder.

Here are the RHD ITB measured flow rates at 28″ and proximate maximum power potential per cylinder when placed in the high velocity section of the intake runner. Remember this is approximately the maximum Hp that each size will support in a highly tuned engine with extensive modifications that uses wave and velocity tuning to achieve high levels of power/L. If your engine is in a lower state of tune then a larger size can be used to achieve good results. An engine in a lower state of tune will require a slightly larger intake because it does not use the wave and high velocities to such a large extent and is better suited to a lower restriction intake. For this reason the correct size can also be calculated taking into consideration the displacement of the engine.

The table below can be used to help estimate the correct size ITB

40mm 265cfm 61Hp 350-500 cc/cyl

42mm 304cfm 70Hp 450-600 cc/cyl

45mm 362cfm 83Hp 550-700 cc/cyl

48mm 408cfm 94Hp 650-800 cc/cyl

Remember!!

1. Be realistic with your power goals

2. It is much better to be a little bit too small than too big



Practical Example
We installed a set of 40mm ITB’s to a standard Bmw m20 325i engine. No other engine modifications were made at that time and this is the result, a nice 18wKw (25wHp) gain from 112Kw to 130Kw.

1B35A0D5-DC74-4A77-905E-1D08B111D9F2.jpeg

It can be clearly seen from the dyno overlay that the previous power curve using the std manifold is always under the ITB power curve so this intake improved the power over the WHOLE rpm range not just over the top end. The top end is where most of the gains were seen. This should always be the case if the itb system is designed correctly, if gains were only seen at the top end or quite often no gains were realized at all then the chances are the system is too big and optimum runner velocity was never reached



RUNNER LENGTH
This brings us to the second important aspect of the intake which is the length, this is actually quite simple there are harmonic frequencies in the runner caused by the pulsing effect of the induction stroke and these are set by the rpm. There always needs to be a high speed section in the port of adequate length for the air to develop enough kinetic energy so this eliminates the last group of harmonic frequencies and the second is typically too long to be practical and wall friction losses would diminish its effect. After that comes an optimal length for any given rpm ande some secondary lengths either side which also work well and will cross over at lower and higher rpm”s. A simple rpm based chart can be used to determine the correct length where you want your engine to operate. So it goes to reason that if you have an unmodified engine with low power output you would use an appropriate size itb probably quite small in diameter and a long runner and this will help that particular engine perform at its best regardless of the engine modifications.

EAF818D4-F866-4A84-ACDF-3F9DE0E47C70.jpeg

1346B81A-9E0E-4D30-ABFE-7EA5CF7738DC.jpeg

[nolastyankee]

Simply put, I put a nearly identical setup on a Ford small block in my 289 Cobra (replica) and have spent years questioning that decision. Initially I was drawn by the killer stack looks and promise of EFI simplicity. Reality - it's definitely not a drop and go, and given that there are not many of these out there plan on being on your own to get the system dialed in. While the EFI promise is definitely possible, especially now with better tech than I had 10 years ago, there are some realities that the manufacturer won't tell you that are absolutely real.

IMG_0088.JPG

1. EFI systems need a robust "power demand" signal. Most EFI runs on a common plenum system where the needs of all cylinders create a strong and balanced pull. On individual runner ITB's there are a couple options:
A micro plenum can be created in the manifold (requiring a custom manifold or retrofitting something like the water tube in a U20) - Pro: replicates most common tech; Con - micro plenum signal is very touchy
Or system can operate from throttle sensor approximating vacuum - Pro: more linear signal; Con - artificial signal, requires much more tuning.

2. Budget at least a full day on the dyno. Also, make sure your dyno tech knows your software and hardware since there is not likely a baseline tune to borrow from another similar engine. Because stack systems are not the most common, and are generally not packaged with included software (i.e. an Edelbrock solution) expect a learning curve on your dime. We had an Accel DFI tech drive in from a nearby drag race to tune the Cobra, we got it close in a day but really needed 2. Plan multiple days if you want to get into dialing in each cylinder.

3. Realistically assess your electrical engineering skills. You will need to be an expert in reading wiring diagrams, soldering, installing and packaging stuff that never existed on the car. Plan to make a bunch of brackets to adapt for mechanical interference you didn't plan on. Also be ready to chase down that one single questionable solder joint in the hundreds you installed. My system added to the car a throttle position sensor, idle air sensor, idle air adjusting motor (choke), ambient air temp sensor, exhaust has temp sensor, an electric fuel pump, fuel pressure regulator, 2 fuel rails, 8 injectors, and a fuel return line.

4. Plan to be on your own. Yes, the manufacturer will be helpful, and not nearby to see what you are seeing. Given the Datsun community is small there are likely only a handful of others on a similar system, and odds are the engine and software combo will not be the same limiting the help factor.

In the end, if I were not $7500 and tons of install into the EFI on the Cobra it would be on eBay and I would have Webers. After all the work the Cobra is a monster when it is warm, but has gotten really fussy when cold and I know I have a month of troubleshooting to find the cause.

Please do not take this as discouragement - just a cautionary tale from someone who at one time was in the same place with the same ideas as I see here.

[fj20spl311]

Copying a good article on the subject

An engine in a lower state of tune will require a slightly larger intake because it does not use the wave and high velocities to such a large extent and is better suited to a lower restriction intake.

Very good article! But this worried me, because it implied you should go bigger....

Remember!!

2. It is much better to be a little bit too small than too big

All is better.....

I don't know the CFM numbers for a U20, but consider its a 2V per cylinder and most newer motors at 4V which flow much better.

I would suggest starting at no more than 40 mm.

If I ever install my 45 mm ITBs on my FJ20, I will try install a DOCE choke above the throttle plates.

[Daryl Smith]

"I love the look, but I am concerned they are not available in taper bore or with some sort of venturi."

Phil,
I have heard this about a "taper bore" a few times over the years....Don't really know where it comes from, would like to find some more information, if you can point me in the right direction...?

That being said, an article I posted a couple years ago on 'bellmouth' shape did not mention anything past the bellmouth (http://www.nsxprime.com/w/images/9/9e/% ... ._2006.pdf) . Vizard's book on the A series engine has a section on bellmouth shapes, and concluded that the best was a 'stub stack'....looking at (and cutting one open) some OEM efi manifolds, the runners were long and parallel. Also read in passing somewhere recently where a 'parallel' runner was key to building velocity (but can't find it again...no mention of length). This info has led me to ignore any taper bore worries, and concentrate on correct diameter, length, and bellmouth.
If you read the Blair/Cahoon article, there is only a very small difference between a simple radius bellmouth and the optimal, doesn't seem worth chasing unless you're in the upper end of racing....

Venturi? Bellmouth entry, parallel runner, opening into valve bowl/throat area...does that qualify? As far as fuel mixing, modern injectors spray a good fine mist which is expected to mix very well...

Agreed on thks for posting those articles!

Cheers

[fj20spl311]

Daryl

Jenvey UK offers tapered bore Throttle Bodies

I sent them an email to see if 40 mm Heritage DCOE Twin body are available and can they taper bore them.

[princeout]

Phil,
Let us know what you hear from Jenvey. 40mm sounds about right based on a brief reading of the above posts.

Thanks to all who have posted!

If anyone comes across any info on an actual installation on a vintage auto, post a link.

Thanks,
Tim

[Pjackb]

If anyone comes across any info on an actual installation on a vintage auto, post a link.

Thanks,
Tim

Enjoy
.
https://www.pressreader.com/uk/vantage/ ... 0880638692

[princeout]

Thanks! My only experience with Aston Martin's was almost being run down by a DB5 while walking across the street in Denver back in '80...

Tim

[princeout]

Digging down a little to the ECU mentioned in the Aston Martin article yields this "kit" listed on the Emerald website:

Convert existing 4 cylinder carburetor engines to Throttle bodies - 4 cyl carb kit
(ideally those engines previously fitted with twin DCOE carbs)
Emerald Generic K6 ECU *
Flying loom on ECU plug - inductive crank sensor
2 x Jenvey 45mm DCOE Twin Throttle bodies
Jenvey Fuel rail kit
Emerald Adjustable Length Intake - set of 4
Fuel injectors - 320cc's - set of 4
2-pin mini timer plugs - set of 4 (for fuel injectors)
Adjustable Fuel pressure regulator
Sytec fuel injection pump -5 bar nominal pressure
Throttle Position Sensor & plug
Air temperature sensor & plug
Coolant temp sensor & plug
Emerald 36-1 crank trigger wheel, 5 spoke 165mm
Marelli crank position sensor & plug
Ford 4 cylinder Gen2 coil pack & plug

Emerald K6 throttle body conversion kit, carbs to fuel injection - 4 cyl carb kit - Price - £1,595.00

Also says it is out of stock and seems like the Jenvey site was also out of stock.

Almost $2,100 at today's exchange rate. More food for thought.

Tim