You are almost there The VL/VLT fuel pressure regulator maintains *constant* pressure across the injector regardless of manifold pressure. If you measure pressure across the injector then the VL/VLT is *not* a rising rate, if you measure from rail to atmos then it is. It all depends where you measure - but bear in mind *all* fuel pressure regulators that are standard equipment on fuel injected cars for last 20 years are therefore 'rising rate' if you only measure fuel rail to atmospheric. In my book this is *not* rising rate - because the pressure _across the injector_ doesnt rise with absolute manifold pressure. Please have another look at the context of my previous post. Its not a matter of agreeing to disagree - I am reflecting the contents of the blue book GMH service manual and I am using the correct definition of 'rising rate' as it applies to pressure across the injector and I have confirmed this in practice by using a differential gauge. The same situation exists for the naturally aspirated engine. At Idle the pressure across the injector is say 250KPa when manifold is something like 10kpa absolute. When you go to Wide Open Throttle (WOT), the pressure across the injector is still 250KPa even though the pressure at the manifold is almost 100Kpa. This confirms you can use the standard VL fuel pressure regulator in the VLT with no problems at all - provided it is plumbed correctly into the manifold and it isnt duff. So then, one might ask - what is a *true* rising rate regulator ? Well the answer is simple. It is very similar to a standard VL/VLT but *adds* more pressure across the injector for higher boost as a further enrichment. Now, I dont know in what context people are selling the regulators for the sexy sound of 'rising rate' because they (the suppliers) and some mechanics misuse the term 'rising rate' because they dont specify where the measurement is taken. All EFI fuel pressure regulators (in order to provide correct metering) whether tubo or N/A (in your book) are 'rising rate' from day one if plumbed correctly. So have many people been sold expensive regulators on the belief the VL/VLT is not rising rate - I guess so... Some original photos have not been recovered yet.

as you say the vl/t regs can be described as rrr , but they are inadequate , if running highish boost whilst retaining the stock non-remappable comp , simlpe statement , i had the stock reg , at say 14psi i had quite a lean top end , on with the malpassi rrr , the top end lowered to a much more safe afr. as boost rose so did fuel pres along the rail , more so than the stock vlt reg , thus giving more fuel at injector opening. thats the most common understanding of ppl when they go out and buy a new expensive malpassi or the likes. btw mike - can i ask what u do as a job , u seem very smart with this situation.

The kind of fuel pressure regulator you have mentioned is just a rising rate regulator that rises at a different ratio eg. a standard reg rises at 1:1 but you can get regs that rise at say 1:1.2 (just an example dont quote me on the ratio) but what im saying is its still rising rate. Or you can have adjustable rising rate regs like i have which allows you to turn the fuel pressure up so i can milk a bit more out of my injectors, so now my fuel pressure has gone from 38psi at idle to 44psi at idle but once boost comes on it still rises at 1:1. Quote: If the pressure continues to drop to zero over a few minutes then there is a leak back through your fuel pressure regulator or your pump, either of these indicate a problem if you want maximum performance, most people can live with a little leak back. I still disagree with this quote. If you have a vacuum gauge on a naturally asperated engine then the gauge will read the same at full throttle as it would when the engine is switched off. So if you were to disconnect your fuel pump at full throttle what would your fuel pressure do? It would drop to zero within seconds exactly the same as it would if you switched the engine off. It shouldnt take minutes like you have stated.

I had a standard VLT reg and i was running 22psi boost and it worked fine maybe there was a problem with your regulator OVL-087 cause it shouldnt have been dropping pressure like that. I think you will find theres quite a lot of hypo VLs running more then 14psi that still run the standard reg cause they work fine i would still have one if i didnt need to milk a bit more out of the injectors. The item i have is the same as a Malpassi which allows you to riase your base fuel pressure so you will be running a higher fuel pressure through out but it still only rises at 1:1 the same as the VL regs

Quote: Originally Posted by OVL087 as you say the vl/t regs can be described as rrr , but they are inadequate , if running highish boost whilst retaining the stock non-remappable comp , simlpe statement , i had the stock reg , at say 14psi i had quite a lean top end , on with the malpassi rrr , the top end lowered to a much more safe afr. as boost rose so did fuel pres along the rail , more so than the stock vlt reg , thus giving more fuel at injector opening. Thats fair enough, the bog standard VL/VLT reg is a cheapy made out of pressed steel with prob not much Statistical Process Control (SPC) gone into the spring/diaphragm combination so it may well reach some nonlinear response when pushed too far. I'm not sure though what that limit is - it is afterall a differential regulator and as long as the casing isnt stressed too much I would guess it would work fine for fairly high absolute pressures but then the variation between units may well be significant at higher pressures, this would be why some people report major difference and some dont when going to better regulators, especially since primary air flow sensing is via AFM and closed loop to compensate for pressure regulators is not used on the VL/Bosch ECU at Wide Open Throttle. I'm not sure what the flow rate limitations are but that is likely to be exceeded by almost any aftermarket regulator regardless of pressure range. The Malpassi may well be just better built and handle more flow with more responsiveness to pressure changes than the standard VL/VLT - but I thought it was a *true* rising rate - now I'm not so sure it isnt that different to a standard one. So your experience could well be at one end of the std dev curve with the bog standard VL/VLT reg being inadequate in flow as well as regulation responsiveness... Quote: Originally Posted by OVL087 btw mike - can i ask what u do as a job , u seem very smart with this situation. Well, <cough> I do a bit of design from time to time for all sorts of people and have a knack for cost effective solutions so make a crust from that line of work (sometimes) et-cetera... I'm doing an enhanced aux dash for my VLT at moment, when I get time from client work, should be ready in about 2-3 weeks, one issue is differential fuel pressure so I can really see what the truth is about various aftermarket 'items', with a few other niceties for a 'weee bit' of glitz appeal 8O

Quote: Originally Posted by PSI-03l I had a standard VLT reg and i was running 22psi boost and it worked fine maybe there was a problem with your regulator OVL-087 cause it shouldnt have been dropping pressure like that. I think you will find theres quite a lot of hypo VLs running more then 14psi that still run the standard reg cause they work fine i would still have one if i didnt need to milk a bit more out of the injectors. The item i have is the same as a Malpassi which allows you to riase your base fuel pressure so you will be running a higher fuel pressure through out but it still only rises at 1:1 the same as the VL regs Yeah good point, I've tried about 3 different VL/VLT regulators over a 12 month period and although all were just a bit different they were all usable enough - I dare say there could be some cars out there with marginal regulators and if people had upgraded those to some aftermarket then they would be the most vocal about going to the 'very best' RRR quoting some tradename etc <sigh> Having said that, the pipes on the VL/VLT regulator are a bit pissy and its a basic built unit, most aftermarket units may well offer far better responsiveness - especially to sudden Wide Open Throttle changes which most people seem to want... Also I notice the manifold pipe going to the regulator is not held on with any clamp, even a small pipe like this exposed to 10 - 20 psi might well leak a bit - or rather bypass a small proportion of air just like a bleed valve so the regulator doesnt actually see full manifold pressure at its reference port - this could make quite a big difference at WOT for higher boost - all mine are clamped tight wth vaseline and cable ties, no jokes here ;-)

Mike m if the regs in VL/VLTs are the same, stick a N/a VL reg in a VL running 22 pound and see how it goes.....

haha

Quote: Originally Posted by stoney Mike m if the regs in VL/VLTs are the same, stick a N/a VL reg in a VL running 22 pound and see how it goes..... I've done that on 2 occasions but only up to 11psi, the action is the same and I had a proper differential pressure gauge to see the actual result in plain view. I'm not saying the VL/VLT is 'good' for higher pressure given they are mass produced items and therefore it is likely some VLT (and VL) regulators wont be reliable and have bad responsiveness at the pressures you are running, especially really bad hysteresis and flow. The fact is for the VL and VLT regulators - they both reference to manifold pressure and the construction is identical. Any difference in part number is a commercial issue for Holden :? If I wanted to run 22psi, I'd go for a machined regulator which was adjustable, but *most* VL/VLT regulators are quite happy at 11psi but sure some might not be, this is normal variation for a mass produced item at the limits of its flow - higher spec'd regulators obviously have better range and better attention to statistical tests to refine product quality.

Quote: Originally Posted by PSI-03l I had a standard VLT reg and i was running 22psi boost and it worked fine maybe there was a problem with your regulator OVL-087 cause it shouldnt have been dropping pressure like that. I think you will find theres quite a lot of hypo VLs running more then 14psi that still run the standard reg cause they work fine i would still have one if i didnt need to milk a bit more out of the injectors. The item i have is the same as a Malpassi which allows you to riase your base fuel pressure so you will be running a higher fuel pressure through out but it still only rises at 1:1 the same as the VL regs mine could be ****ty i geuss i have still got it on car and have the malpassi running of it , that way i can keep the base idle pressure correct/factory so as to not toss the computer , but when under wot i can get that wee bit extra from the malp.