🛠 Throttle Pump aka Transient Throttle Enrichment Explained | TECHNICALLY SPEAKING

hi guys today we're going to be unraveling one of the secrets of tuning that's right we often talked about but rarely understood dark art of the throttle pump or as we call it here at haltech the transient throttle enrichment function [Music] now if you've been around engines or engine tuning for more than a minute you've probably come across a vehicle or engine that runs pretty well under steady state conditions at all load and rpm areas but when you mash this throttle quickly the thing costs and splatters worse than a covered ward in winter and then eventually it takes off again 9 times out of 10 the reason for this is the transient throttle enrichment has not been set up correctly now if that all sounds very confusing and you've never heard a conversation around the water cooler about transient throttle enrichment that could be because this feature goes by a few different names now if you're coming from the carburetor world you probably know this term as the accelerator pump or the accelerator enrichment valve or perhaps you know it is throttle pump or fuel tip in or throttle tip in all of these terms refer to the same thing in the how tech software we call it the transient throttle enrichment function in this video we're going to go through the physics of why this function exists in the first place and how to enable it in the software how to set it up and what each of the maps does so before we get too deep into the haltech software let's first have a discussion about what the transient throttle enrichment is and why we need it because this will set us up for a really good understanding of how to approach the tuning process so if we cast our minds back to the ye old days of carburetors you remember that in every car there's a fuel circuit that is activated purely by moving the throttle the way it works is regardless of the amount of air moving through the carburetor when you move the throttle you get an extra squirt of fuel now if you don't believe me take the air filter off a carburetor with the engine not running take a look down the hole and stab the throttle what you'll see is a squirt of fuel get shot into the intake manifold this is the accelerator enrichment circuit in a carb it's quite an intricate balance of springs pistons and valves and you can trust me when i say this carburetor manufacturers do not put them in there for fun and you know if you've ever had the accelerator enrichment circuit clog up or stopped working on your carb then you know exactly what happens the engine starts and runs just fine so long as you're really gentle on the throttle everything's good but stand on that throttle quickly and the engine has a massive lean spot it hesitates it often misfires and occasionally backfires through the carburetor and it takes off but the question is why why does this happen and how does this all relate to an efi system well that's where we have to put our physics hat on for the moment so the key to knowing the answer to this is the lean spot the engine is running fine until you mash the throttle and then it goes lean but why well it's actually simple physics in a carburetor the air and the fuel are both injected into the intake manifold at the same spot the carbi what happens when you mash your right foot to the floor and the throttle blades slam open you get a big gulp of air that rushes into the intake manifold however and here comes the physics air is approximately 600 times lighter than fuel so when you get a rush of air into the intake the air makes its way down to the valve and into the combustion chamber 600 times faster than the fuel because it's 600 times lighter so the next time the intake valve opens the air rushes in the fuel hasn't caught up yet the intake valve closes we get compression and spark but no bang this happens for a couple of engine cycles until the fuel finally decides to show up to the party and we start making fire again so the throttle pump circuit on your carburetor is designed purely to try and give that fat lazy heavy fuel a head start in the race to the intake valve in the hope that some of it makes it there in time for the intake valve opening so if you actually put an air fuel ratio meter on a carbureted engine you'll notice that even the most finely tuned carburetor will always have a lean spike followed by a long rich tail on acceleration you get the rich tail because the regular fuel delivery eventually catches up with the additional fuel in the acceleration enrichment and the engine runs rich for a period of time so what does this mean for our efi systems well the first thing to note is what the limitation is in the carburetor that causes this phenomenon it's the fact that the air and the fuel are both coming into the intake at the same place that's not actually all that common in a modern efi system see typically we find our fuel injectors are located much closer to the intake valve than the throttle body so effectively the fuel has now got a massive head start in the race to the intake valve the second advantage we have with efi is the pressure under which we're injecting the fuel with an additional 40 psi fuel pressure pushing the fuel toward the intake valve we're roll racing versus drag racing here and finally the most modern injectors do a really good job of atomizing the fuel into very fine droplets so they can accelerate really quickly as well so what does all this mean for us with our efi system well put simply it means most of the time we need a lot less additional fuel to be added to the intake manifold when the throttle is snapped now i say most of the time here because there's always exceptions if you're running a throttle body injection setup you tend to find you still need to provide a lot of additional fuel in the transient throttle enrichment because you're dealing with the same limitation that a carburetor has the fuel is still much heavier than the air and because it's a throttle body injection setup the fuel and the air are being injected at the same spot into the intake manifold so we need to throw much more fuel at the race as early as possible to try and prevent the engine from misfiring another thing that can be different in an efi system is using sequential fuel injection and being able to time the fuel delivery event specifically with the intake valve opening now i won't go too deep into this because it's actually a topic that requires more than the available time in this video but what i will say is the injection timing that is to say when the fuel is injected rather than how much of fuel is being ejected often plays a really big part in the overall vehicle drivability which includes the transient throttle setup so the best tip i can give you here is don't put too much effort into tuning the transient's throttle enrichment until after you're happy with the tune up on all of your steady state fuel maps which includes the injection angle map and with all of that said let's lift the hood on the haltec nsp software and take a look at the transient throttle enrichment function settings and the maps available for calibration the transient throttle enrichment setup and maps can be found under the fuel tuning node in the menu tree structure as you can see there are quite a few settings here to set up don't worry we're going to cover them all and in addition to this setup there's also a bunch of maps that will need to be calibrated as well all right so let's crack into it the transient throttle load type lets the ecu know which sensor to look for to trigger the transient throttle fuel correction now i know what you're thinking this is a trick question don't we have to look at the throttle position for this i mean that's what it's called the transient throttle correction right well normally yes but sometimes no there are situations where you have a throttle body that doesn't have a full sweep style throttle position sensor so you only get two positions on the tps closed and open throttle that's it these throttle bodies are really common in early 90s fuel injection systems in this situation we can actually use the change of manifold pressure to trigger the throttle pump it's not as good as using the throttle position sensor if you have a full sweep sensor but it is better than nothing but for this demonstration we're going to stick to the throttle position sensor as the load type now we can enable a disenrichment which is the opposite of enrichment so it's fuel coming out and an overall correction i'll come back to both of these in a moment for now i'll just leave them off to prevent some confusion now the next four setup things are what gets people most confused we've got the load rate dead band the load acceleration deadband the detect duration and the ignition decay time now that's some really propeller hat terminology there so let's take a look at each setting individually the load rate deadband is the speed at which you need to move the throttle before the throttle enrichment is activated now remember back to our carbi car it drove fine if you were gentle on the throttle and it only stumbled when you stabbed that throttle quickly well the same rules apply here and this is the setting that tells us the throttle movement speed below which no correction is needed now as you can see the units of this setting are percent per second and with a value of 25 in the load throttle deadband i've got to move the throttle more than 25 in one second for the transient throttle enrichment to be activated now that's what it means so as a rule of thumb the larger the throttle area the lower this number needs to be which of course makes perfect sense because all things being equal when you put a larger throttle on an engine to get the same amount of air into the intake you don't need to open the throttle as far if you're running individual throttle bodies for example it's not uncommon to see this load rate deadband number as low as 25 percent on mild cam single throttle engines it can be up over 150 that gives you a range to work with on to the next setting the load acceleration deadband is the speed at which you need to keep the throttle moving for the throttle enrichment to stay active so the easiest way to think about this setting is it's the length of time the additional transient throttle fuel enrichment is being delivered for longer injection durations then you would use a smaller number here larger numbers give you a shorter duration so in a throttle body injection setup for example you might use a load acceleration dead brand of around 50 and in a more modern engine with the injectors down near the valve you need a much shorter duration so a load acceleration deadbend of say 200 might be more appropriate next up we have our detection duration now this is the amount of time the ecu looks at the throttle movement to determine if the throttle movement is real or noise a smaller number is more prone to false trips but reacts a little bit quicker too long and there'll be a delay in the fuel delivery typically i would normally set this value to between 5 and 10 milliseconds then we have this enable async button now if i turn this setting on i get a couple of more settings and another map to tune but what does this async injection mean well put simply this setting tells the ecu to deliver some fuel to all of the injectors immediately when the throttle pump is triggered think of it a lot like that carburetor circuit you move the throttle you get more fuel now that all makes sense but let's remember for a moment unlike a carb most modern efi injection systems spray fuel directly at the valve at a very specific time in a sequential manner so there are two possible ways the ecu could deliver the extra fuel required for the transient throttle enrichment we could simply extend the next programmed injector pulse and time the fuel delivery with a valve opening we will call this synchronous injection because it's synchronized with the next injection event or we could just pulse the injectors as soon as we see the throttle move that's called asynchronous injection because it's not synchronized with the next injection event now obviously if you're not running sequential injection your best results will come from using asynchronous injection but if you're running sequential injection you can normally get better results from synchronous injections so just extending the next pulse that's not always the case however engines with big camshafts and a lot of valve overlap often require a good amount of both synchronous and asynchronous injection to be snappy it is what it is okay so let's assume for a moment that we have our engine set up and running and tuned really well in steady state and now we actually want to tune the transient throttle enrichment maps so we snap the throttle it moves faster than the load rate deadband value so the ecu decides yes i need to inject some additional fuel into the engine there's two questions that these you ask yourself one how much fuel do i need to deliver and two when and how do i need to deliver it and all of that depends on the combination of what you've programmed into the injection rate map and the injection amount maps for both the synchronous and asynchronous enrichment let's take a look first at the enrichment rate map now the first thing i'll note is that both the synchronous and the asynchronous enrichment amount maps refer back to this one enrichment rate map so in simple terms if we had 50 percent in the entire enrichment rate map and 100 over in the entire synchronous enrichment amount map when the transient throttle enrichment is triggered the ecu would extend the next injection pulse by 50 okay how did i work that out well my rate map said to add 50 more fuel to the next injection event at the particular rpm i'm at in the synchronous enrichment amount map i've said we'll apply 100 of that correction so the ecu extends the next injection pulse by 100 or 50 which is 50 more fuel now if i had all the same settings but rather than having the synchronous enrichment amount set to 100 i had it set to zero and the asynchronous map was set to 100 then the ecu would still attempt to inject the same amount of additional fuel which is 50 more but rather than just extending the next programmed injector pulse the ecu would immediately pulse all the injectors for the calculated injection time if i had 100 in both maps which is possible the ecu would do both it would extend the next programmed injection pulse as well as immediately pulse all of the injectors so they were the easy to understand numbers let's look back at the base map setup and see what the tables actually look like so opening up the enrichment rate map we have two axes the y axis has the throttle start position and the x-axis has the transient throttle load derivative which in layman's terms is just how fast you're moving the throttle so the reason this is a 3d map is because you could be sitting at the mcdonald's parking lot stabbing the throttles from idle to impress the local law enforcement or you could be barreling down the strait coming into turn three of your local race track at 25 throttle and 4000 rpm and just leaning on throttle on the way out of the corner both conditions will require an amount of transient throttle fuel enrichment but totally different start positions and a totally different amount of additional fuel which is why this map exists as a map the y-axis is the start throttle position the x-axis is how fast you're moving the throttle so you can see in the base map the lower the throttle angle to start with and the faster you stab the throttle the more additional fuel you need now we've also got an ignition correction map that's often used in conjunction with the transient fuel enrichment map and i know this is an ignition map not a fuel map but the reason some tuners like to use this map is that the big gulp of air that rushes into the engine can cause the engine to knock for just the moment when the throttle is stabbed quickly and under high stress conditions now we normally only see this on high compression not limited engines but the phenom is real which is why this map exists and finally we've got a coolant temp correction map now basically when the engine is cold much of the fuel delivered to the intake manifold pulls on the intake manifold walls so if the engine's cold we need a bunch more fuel in the transient throttle enrichment map the further the injector is away from the intake valve the more coolant temp correction will be required alright so now we're armed with a little bit of background information we can begin to tune this map up on an engine and this is where i actually get a lot of questions how do i tune the throttle pumps and what am i aiming for and with all things tuning the answer to that one is it depends so on a race car my aim is to have the engine be snappy and not have flat spots when the throttle is pressed on a street car where maybe emissions are going to be required i'll often slow down the throttle opening so that the transient throttle enrichment is actually not required at all because that extra fuel equals excess hydrocarbons which may mean failing an emissions test the other thing i would say is before i even touch the transient throttle enrichment i'd make sure that i'm happy with all of the other fuel mapping parameters and that the engine is running really really well which includes tuning the end of injection angle for either maximum torque or the richest fee ratio again i'm not going to talk about it too much but trust me that does make a difference now only then would i look at mapping the transient throttle now from here my process would be if the injectors are down near the valve i'd turn off the asynchronous injection completely and i'd rely solely on the synchronous injection then i'd go into the enrichment rate map and i'd stab the throttle as quickly as i can a couple of times and i turn the trace mode on while i'm doing this now this is going to show me what cells in the map are possible for me to get to so at least i know what i'm possibly working with and from here it's really a process of make an adjustment and feel how the engine responds now you can also use the air fuel ratio as a reasonable guide to how you're doing now you don't want to see the fu ratio sync to ten to one and then stay there for five seconds every time you stab the throttle but don't worry too much if there's a little peak in a trough if the engine sounds good responds well and dries well that's what you're looking for go with what the engine is telling you i know this is a complex topic and there's a lot of moving parts so understanding the fundamentals of why we need this transient throttle fuel enrichment does help in the setup and tuning of the engine the underlying physics of fuel being heavier than air and therefore the air being able to accelerate faster than the fuel means that the further the injector is away from the intake valve the more additional fuel will be required in the transient throttle enrichment maps where the fuel injection is not sequential and therefore it's not timed to any intake valve opening asynchronous injection works best where as soon as the throttle moves the ecu injects the extra fuel into the manifold from all the injectors the faster the throttle is moved the bigger the gulp of air and therefore the more transient throttle enrichment is required and finally the higher the engine rpm is to start with the less additional fuels required so hopefully this video has given you a little bit more understanding and insight into how to approach your transient throttle enrichment maps now if you're paying attention then tell us in 10 words or less in the comments below the difference between synchronous and asynchronous injection types and the first three correct answers we'll get a free pair of these cool healthtech workshop gloves if you liked the video don't forget to ring the bell icon for notifications on all of our latest youtube videos if you haven't already subscribe to our monthly newsletter go ahead and do that now to find out about all the latest product offerings and of course give us a follow on all the social media channels well that's all i've got time for today i'm matt from healthtech and i'll see you next time [Music] you

Channel: Haltech

Views: 28,135

Keywords: haltech, ecu, engine management, tuning, engine tuning, technically speaking, volumetric efficiency, ve, tuning using ve, ve tuning, tuning tech, tuning tech tips, internal combustion engine, four stroke engine, tuning basics, programmable engine management, tuning a car, ignition tuning basics, how to tune a car, how to tune, efi tuning, throttle pump, acceleration enrichment, transient throttle enrichment, acceleration enrichment tuning, haltech tuning software

Id: DMT9kVO7fUU

Length: 21min 50sec (1310 seconds)

Published: Fri Oct 01 2021