depends on the type of transition. In the part throttle stuff and transition to where its near useless to derive something from math. On the longer WOT sweeps would stabilize.. But you could starve for 50% of a lap before that happens.

I considered an AFR warning but my only gripe with that was that when you start starving your getting an average across all 4 cylinders out of the wideband so its not as reactive as I'd like it to be.

The FIC 2150s have been said to be a great injector. Tom @ Ecmlink runs them in his DD and well as many others but I would say getting in touch with FIC about your setup would be the best way. I am sure they will have the best information for you and its hard to tell you what injector is best because it is so dependent on fuel pressure.

Might I ask what F.P are you going to run. If you ran a higher fuel pressure than the rail was seeing when you were using the rising rate regulator at full boost you would increase that injectors flow. Its a 1:1 ratio so at your 30 psi of boost you should be around 73 psi at the rail. If you increased that to somewhere around a walbro 255's max fuel pressure which is around 85 psi you would get quite a bit more flow out of the 1600s your running and a hell of alot more if you stepped up to even 100cc bigger(100cc measured a 3bar). I would be very interested to see more information on the setup. I didn't notice you posting this on NABR.

Thanks for the reply.

If I had 2150s for example I could run some thing in between the 73psi I was seeing and the base pressure of 43 I am running now. My compromise/goal was to be in between the control range minimum of the ECU and trying to keep the bosch pumps from working too hard. They have a limited life span rating as it is on alcohol.

I try not to spam NABR with all my little projects haha

ID 2000s are the best injectors for big power on E85. They are expensive but they will be the last set of injectors you will ever buy for your dsm.

It wasn't a calculator--11 lbs/min is just from conversions. 0.68 lambda (10:1 gas AFR, 6.7:1 E85) shows you to support ~73 lbs/min airflow on E85, which is roughly where you state you are. Knowing that then yeah it makes sense that your IDCs are high. I would agree that 2150's//ID2000's are the way to go for you.

I'm using two rails and two sets of injectors. I think that you may like it. I use the smaller injectors for low end and initial boost. The seconds come in and take care of the rest. I am not sure about the your tuning system, but using the aem is okay. My buddy and I are both using 8 injectors with no problems.

nek said:

Btw, How did you enjoy tuning those bosch 1600's. I grabbed a set for a steal but Ive read they are a pain!

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Thats interesting, they had worked really great for me. What kind of problems are you having?

gixxerdrew said:

depends on the type of transition. In the part throttle stuff and transition to where its near useless to derive something from math. On the longer WOT sweeps would stabilize.. But you could starve for 50% of a lap before that happens.

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If your fuel pressure bounces around that much, it almost sounds as though you need a better regulator or higher flow pump. Can you email me a screen capture of this, so I can understand exactly what it is you are looking at?

^My thoughts as well. I hesitated to post that however since I didn't want to reopen the static fuel pressure debate.

I would suggest replace/repair the FPR, and if that doesn't correct the issue, then I'd plumb in a robust inline just ahead of the rail.

I'm just lost as to how you can have that much trouble. Obviously I'm a couple hundred whp behind where your at now, but I've never ever had an issue with latency in my fuel pressure. I run a 255hp, and a stock n/t fpr. Obviously I have some overrun at idle, but thats not the issue you have. I also run stock lines and filter with FIC 750's and make 460whp on E85. I also don't have the safety cushion you have either.

Hell, I used to run my 255hp with a shimmed n/t fpr to get my base up to 65, and still didn't have problems, even running 25psi boost.

I'm fairly confident that the issues you see are not caused by having rail pressure track manifold pressure. You probably just don't have enough pump to support your requirements.

Well I'm guessing you are not running a DAQ system and trying to derive a math channel on the basis of system response? that might explain why I have a problem and you dont.

Let me explain a bit of background. I'm using high accuracy Kavlico sensors and logging at 200hz. I have done this on say... maybe two dozen cars and I have never in my career as a professional race car data guy seen a car that didnt have lag in the response of fuel pressure regulator.

Fuel pump overrun is totally different on a log than response delay. You see the fuel pressure drop (on the far side of the rail especially) as demand increases. Latency is exactly the opposite, it doesnt ramp up as fast as manifold pressure ramps up. I have always seen a physical lag there on every car, including this one.

delta448 said:

^My thoughts as well. I hesitated to post that however since I didn't want to reopen the static fuel pressure debate.

I would suggest replace/repair the FPR, and if that doesn't correct the issue, then I'd plumb in a robust inline just ahead of the rail.

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I gotta disagree, I log a lot of cars, FPRs have always been laggy from what I have seen. They are not super laggy to where your car tune is going to have "an issue" they are laggy to where you cant derive a math channel well from the delta to warn about starvation.

The lag in a regulator system is basically a fact of life, theres lag everywhere in the system. The system never needed to be any better than for tuning and AFRs to be consistant.

For tuning its pretty much a non issue anyway because the system response all gets wrapped up in your tip in compensation in the ECU. Even when you open the throttle plate there is still a lag there before that pressure change reaches the combustion chambers, you are still moving a physical fluid. My $.02

Im trying to dig through my old DAQ system logs to get a screenshot here for brad...but I'm having trouble finding a log because none of the cars I log use rising rate fuel pressure or are normally aspirated, ALMS, SuperGT, Rolex GT... every log I have. Even the motec sample car uses static 70psi rail pressure and 1 bar boost. But even that log is a tenth of a second lag for a 2psi variation in response to a load change. Is it so difficult to believe that a 43 to 73 psi response could two tenths of a second to respond to?

edit: Brad, I sent you a message off site with a screenshot

they are laggy to where you cant derive a math channel well from the delta to warn about starvation.

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Please forgive my abundant ignorance, but I seriously doubt I'm fully grasping your objectives. Your terminology is confusing the crap out of me. I don't expect you to be remedial with me, you're the expert here not me.

But please do forgive me when I ask a dumb question, -is this thread all about setting up a warning in data acquisition to tell the team when the pump is not keeping up? If so, then why not simply set up a safeguard? Maybe an additional pulsewidth adder, per cylinder per load when there is a delta pressure over the rail length? ECU response surely would be quick enough to counteract a fuel pressure lag. Or am I completely missing the point?

The lag in a regulator system is basically a fact of life, theres lag everywhere in the system. The system never needed to be any better than for tuning and AFRs to be consistant.

For tuning its pretty much a non issue anyway because the system response all gets wrapped up in your tip in compensation in the ECU. Even when you open the throttle plate there is still a lag there before that pressure change reaches the combustion chambers, you are still moving a physical fluid. My $.02

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Yes, I can understand and agree with all of this. And tip-in vs a safeguard pw adder is the same concept again as it's using an ECU control to counteract a physical limitation.

delta448 said:

Please forgive my abundant ignorance, but I seriously doubt I'm fully grasping your objectives. Your terminology is confusing the crap out of me. I don't expect you to be remedial with me, you're the expert here not me.

But please do forgive me when I ask a dumb question, -is this thread all about setting up a warning in data acquisition to tell the team when the pump is not keeping up? If so, then why not simply set up a safeguard? Maybe an additional pulsewidth adder, per cylinder per load when there is a delta pressure over the rail length? ECU response surely would be quick enough to counteract a fuel pressure lag. Or am I completely missing the point?



Yes, I can understand and agree with all of this. And tip-in vs a safeguard pw adder is the same concept again as it's using an ECU control to counteract a physical limitation.

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Delta, sorry if I came off frustrated or something. Sorry if the terminology is confusing. Let me try to explain what I believe is going on.

The thread wasnt supposed to be about that, but some respondents started moving off topic and focusing on telling me that something else was my problem that was not a problem and it ended up on this topic. I probably shouldnt have mentioned anything else except asking for experience with larger injectors. I was trying to avoid spending a lot of time writing a long winded explanation like the one below. But here goes.

Any safeguard that worked would make me happy, but I want the best possible safeguard. For example a low level warning in the surge tank wont work that well because you could still fail a pressure pump and not have a warning system.

I'm not sure how an ECU response system would help, but maybe Im not understanding your suggestion? The reason I say that is because I was trying to illustrate that right now there isnt a very clear way to know for sure that the system is in starvation. So any ECU response would run into the same limitations I am discussing here. If the ECU can know it needs to respond it can also just throw a warning light which is really what i am after. no? Something that warns the driver either a pump is dying or we need to add fuel, etc.. as long as we protect the engine in the best possible way. Engines are $10k roughly and losing one will end our racing for probably a year, so we dont want to do that.


Every feedback (control) system has rate of change (and I think this is a feedback system controlling fuel pressure against manifold pressure). It has to, even "instant" electrical systems are not instant at all and take a lot of work to get their response time working well vs overshooting vs oscillations.

For anyone reading this that wants to learn more about that, do a google search on "control systems".

Here is a good physical example: If you have a blown shock or missing shock absorver in a suspension the car bounces all over the place. Until the friction is enough to stop the oscilation (bouncing). The friction caused by bouncing the car up and down provides some damping and the mass of the car causes it to take some time for the force of the spring to accelerate it.

If you use a stiffer spring, the oscilation is faster (more force). Conversely if you increase the mass of the sprung object (car in this case) the oscillation slows down. Because the cars motion is a function of work and the springs rate is a force. The damping since you have no damper is primarily friction, with the air and whatever other things resisting the cars motion to bounce.

The end result is that the car oscilates up and down until the damping has absorbed enough energy and it comes to rest. So to prevent oscilation you NEED damping, like a shock absorber. But if you have ever tried to compress a shock absorber you will know that resists the motion, it slows down the rate of change.

The minimum damping amount needed to keep it from oscillating is called critical damping. Damping it more than you need to prevent an oscillation is called super-critical and damping that still is not enough to stop oscillation is called sub-critical.

Going back to the fuel system, you have an FPR its trying to respond to changes in manifold pressure. It has its own inherent damping to the system it may have been designed to have a certain amount of damping or just natural damping (like the friction of the car bouncing in the air) but no matter what, it is physically impossible that it has no damping at all because it will have some even naturally. The damping is not bad, you want it, because it also keeps it from oscillating too much or overshooting (meaning that after boost stopped rising the FPR keeps raising pressure that exceeds the target).

So heres the crux of this... if you take a math channel (DAQ terminology for a calculation against an input or set of inputs) it will produce bad information telling you if your hitting targets unless it can compensate for the lag or ignore transitions.

Lets say that your base pressure is 43psi. So if you had a perfect pressure regulation system you would have a formula like this:

Manifold Pressure + base pressure = rail pressure.

30psi manifold , 43 psi base

30 + 40 = 73psi at the rail. Simple right?

In theory, yes that would always correlate with perfect fuel pressure regulation. So, lets introduce the system response time and damping.

Since the system has an inherent response time you have these split seconds where say boost is coming online and pressure regulation is responding. Say you exit a corner at 5500rpm and you NAIL the throttle hard. Suddenly in the span of 0.2 seconds you go from 0PSI at the manifold to 30psi at the manifold. The intake system (turbo) response time is 15psi per 0.1 seconds in that case.

But lets say your FPR system only reacts at 5psi per 0.1 seconds. It will take you 0.3 seconds for the fuel pressure to match the manifold pressure but your turbocharger hit its target in 0.2 seconds. You are never going to get them to react simultaneously, give up now.

Why? Well for one a turbos response time depends on a million things, how fast you hit the throttle, at what RPM? so many other variables that have small influences. The FPR systems response time is also dependant on many many variables, current injector load, fuel pumps, volume of the system, air in the system compressibility of the fluid, temperature, contaminants, whatever. Even the fuel rail itself flexing under the load of 75psi of fluid pushing on it. And you can probably imagine how a system with 300% varying pressure on the fuel side is even more unpredictable.

Heres how the real math will look like... you have response time of the turbocharger to provide boost that is 15psi per tenth of a second and fuel pressure regulation system that responds at 5psi per 0.1 seconds:

Then at 0.1 seconds into your going wide open you will have manifold pressure at 15psi but in that time span the fuel pressure system only responded by 5psi. So suddenly your math equation reports that fuel pressure is not where it should be.... NIt thinks that fuel pressure is at -10psi from expected. Because rail pressure has only increased 5psi so far and manifold is up 15psi. So if you had that connected to a warning light you have a driver going what the hell is wrong with this light it turns on all the damn time whenever Im getting in and out of the gas and he starts ignoring it so he can do his job. Drivers dont like complicated stuff, their job takes intense focus. Of course, you can try and filter the math down but at the end of the day your just making your data less reliable if you do.

To make matters worse, when you get into larger pumps you start to see pulsations in the pressure as a natural tendency of those types and size of pumps. So a lot of race cars use "pulse dampers" as well. Pulse dampers are just accumulators so they will also inherently introduce lag to the system just like we explained dampers do, that is their job.

On a road course, you spend a lot of a lap with a moving target manifold pressure. The FPR system is always bouncing around and the more you filter the data to ignore transitional periods the more useless it becomes.

Even in a fixed fuel pressure environment you still see oscillations in the pressure but your math gets MUCH simpler and more reliable. Your total variance should be just 2-3 psi. If you see more than a few psi drop for a time span more than a few tenths of a second (or whatever your lag time is) you can throw a warning that stays on and you will have successfully protected your engine. You'll hit one hiccup and bam the driver pits in when the "pit now" light flips on.

Trouble tends to be progressive so if you catch it early and you have a nice safety margin on your tune and the motor can go forever like that running your tank down to the last drop constantly.

So if you want to do that, run a fixed pressure, whats the problem? pump load? ECU ability to control, injector range?

OK say I have to have 4 bosch pumps on the pressure side so that they are nice and happy at 80psi or whatever. Or i need to put them in series so that they not seeing very high pressure ratios. I can design that system any way I need and pumps are cheap. Engines are not and Ill have exactly one shot at that.

If I get the pump config wrong but my warning system was good, I'll know as soon as a pump is dying or being over-run.

I dont really care what my fuel pump flow requirement is, I can make it happen.. If I have good logging and warning system, I have very low risk. Right now at the pressures we are talking about, if the specs for the pumps are right I have some 20% plus excess in capacity as the system sits.

So the only real limitation is the dynamic range needed in your injector control and if your ECU can hack it, so obviously yah I intend to make sure that the injectors I decided to go with after asking for recommendations will need to fit that bill as well, thats easy, just math. So thats why I was asking about experiences with the monster injectors.

Obviously the injectors work fine at 75+ psi, most of us are running that much rail pressure every time we are on boost.

It's possible Im just asking for too much dynamic range, if thats true so be it, but thats why Im looking into injectors that might fit the bill first. I know that my 1600s have enough range if I keep the boost around what it is now, but I want to see if I can do it AND hit my road course power goals. I dont care if I need to idle at 2500 rpms, thats not a big deal to me.

I just put some id1ks in my dsm and they have great responce from what ive seen sofar. While on the phone with t1 i asked about the bigger 2200cc ones and e85 and i was told that those unlike the 1000cc ones should be flushed with gas if the cars going to sit for some time..just something to keep in mind 100% useable with the e85 just may need drain or flush..

Thank you for the excellent post Andrew. Completely covered my questions with extra to spare. I do understand now. Thanks.

I will bow out now, only adding my vote for the FIC 2150's.

What fuel rail ID do you run?

Have you ever done any logs with using the vacuum signal directly off the turbo vs the intake manifold to the FPR?

Never done it like that. I would imagine the goal would be to get as close of a reading to the intake ports as possible. My rail is 5/8" to match -10 AN line

delta448 said:

Thank you for the excellent post Andrew. Completely covered my questions with extra to spare. I do understand now. Thanks.

I will bow out now, only adding my vote for the FIC 2150's.

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Your welcome,thanks for helping out in the thread.

gixxerdrew said:

Thats interesting, they had worked really great for me. What kind of problems are you having?

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I actually still havent installed them yet, Ive been reading up on them though.
I own the white tops ending in 846. I talked to FIC and they told me
" They are old fat body Bosch 1600cc injectors. (The ones with lots of idle problems), they potentially work OK if you have a clean injector signal. Tuning for gas is a major challenge for the old 1600cc inj! Those a VERY short pulse widths at idle and part throttle. Likely that the injectors cannot repeat them consistently, and that’s why the resulting roughness is hard to tune out" (chopped from email)

Ive also been following a fellow members thread on tuning them, apparently its been updated since.. Take a look!
http://www.dsmtuners.com/forums/tun...tes-bosch-1600cc-injectors-ford-chrysler.html

LMK

gixxerdrew said:

depends on the type of transition. In the part throttle stuff and transition to where its near useless to derive something from math. On the longer WOT sweeps would stabilize.. But you could starve for 50% of a lap before that happens.

I considered an AFR warning but my only gripe with that was that when you start starving your getting an average across all 4 cylinders out of the wideband so its not as reactive as I'd like it to be.

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Not sure what your trying to do but I have setup a number of cars with warnings and control algorithms in the following way:

Rail Pressure = MAP + Base Pressure (base pressure is constant; what you set it as)
RP = MAP + BP

If RP >= MAP + BP : do nothing
if RP <= MAP + BP : pull timing... cut ignition, increase injector duty proportionally, etc...

All you need is a fuel pressure sensor, which im sure you already have. This simple little algorithm has saved me a couple times when a pump died/ was on its way out.

Motec will do it no problem.

I just read you lengthy post in which you described the above math that I mentioned. You can always just pad base fuel pressure in the equation to be 1-2 psi different than actual, this will help filter out a bit of the "false warnings".

I think for the most part, switching to E85 or E98 will give you extra wiggle room and forgiveness during the transient times of concern, and that the above simple equation will tell you when something "big" has gone wrong.

Thats amazing, never seen it work on any cars I log professionally. I see few PSI variance on non rising rate and normally aspirated cars with small changes just in duty cycles but I'm happy it works for you

The turbo signal should be a hair faster and in return help your FP transition issue. A 1/4" vacuum line with a signal vs a 3" intercooler pipe at maybe 48" long with an intercooler in it's path then through an Intake port can't have the same response so this might be a cheap test before you go into hours of computer coding.

Car Cannibal said:

The turbo signal should be a hair faster and in return help your FP transition issue. A 1/4" vacuum line with a signal vs a 3" intercooler pipe at maybe 48" long with an intercooler in it's path then through an Intake port can't have the same response so this might be a cheap test before you go into hours of computer coding.

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Thats not really going to help, its not the rate of the intake system response that is lacking. The fuel system lags behind the response time of the intake system as it is. Fuel system is slower of the two. Also the intake system response is always variable depending on conditions of throttle application, RPM, etc. Its not the same every time. The fuel system is dependant on a whole bunch of very different factors so just making it faster or slower wont resolve the issue.