For some time I have been reading threads about its too laggy etc etc etc and wanted to know what the gurus actually class lag as. Is the consensus that lag is the same term the yanks use when they call it spool i.e the point in the rpm range when full boost potential is achieved. What is the exact criteria people use when deciding if something is too laggy Cheers J
dr concise collins thinks it is ...... ... 4. the interval of time between two events, esp, between an action and it's effect ... for a t/t zed ..??? ... perhaps hitting the accelerator/gas (the action), then the interval (delay) before the turbos hit peak (the effect) .....?????
Corky Bell: Lag: The delay between a change in throttle and the production of noticeable boost when engine rpm is in a range to which boost can be achieved. Boost threshold: This is the lowest engine rpm at which boost will increase power over the engines atmospheric equivalent. In general, lag seems to be classed as the latter when talking about turbos being too "laggy"
what i consider lag is where the car feels like a slow peice of crap them wham on comes boost.. big turbos usually dont progress smoothly.. they off boost.. WHAM full boost check out russel floyds dyno graph for example.. his packing 2 td06 20gs.. very laggy turbos.. but he has extreme engine work to push em.. until 3500rpm his car has less power than stock.. at 3500rpm he only has 100hp.. where scottys car (zweett) for example has(should i say had) 200.. but then the graph takes a vertical step where his over 500hp by 4500rpm.. this is where the turbos kick in.. they dont reach full boost till somewhere around 6000 where full boost is achieved as tourque falls off here.. but that vertical rise is where the turbos step into theire efficiency range for the airflow being received by the turbine... its where this onrush of acceleration comes in that is important.. stock turbos start singing about 2000rpm.. you know... you can feel when the turbos kick in.. when the car starts pulling.. laggy turbos the delay to this point is longer. full boost is irrelevant
It's all relative If I understand your question correctly you're not asking for the definition of the term but rather what constitutes to much lag (in our vehicles?). I once drove around in a Turbo VW (diesel) for about a week. It must have had a really small turbo because that thing would spool up so quick it had almost zero lag. The car felt like it was even more powerful than my zed until you got to the higher revs where the power starter dying off and you soon realized it's missing a big part of the power band. After having driven the VW for a week I got back into the Zed and it felt so odd. For the first time I could really notice the lag, it was sooo much worse than I had even noticed before. This is what really made me notice what a disadvantage lag is on a street car. However, on the track lag is less of an issue, and even less significant on the drag strip were you're on boost most of the time. But on the street it's a lot more noticeable and inconvenient. Lag is obviously and issue as there are many companies out there trying to develop ways of reducing or eliminating it. Apparently there are new technologies on the way which will help reduce lag. Electrically assisted turbos are currently in the testing phase which will help reduce or even eliminate lag for turbo cars, There has also been a handful of production cars from different manufactures which were both turbo and supercharger assisted. The supercharger would only work in the lower rev range until the turbo kicked in after which the supercharge would be disengaged either via a bypass valve or a clutch (similar to the aircon compressor) Variable vane technology is currently available and is being used on the latest Porsche turbo. This technology has been specifically designed to reduce lag. When, or rather if, I ever decide to rebuild my engine most of the focus will be on minimizing lag. As for power I think around 300rwkw is sufficient although I would not say no to more power so long at I?m not compromising responsiveness, i.e. increasing lag.
Yeah thats right Z-ster and also different opinions from peopel as to what think lag is in there own mind. Personally I agree with your statements and others above however. To have a responsive turbo in the lower rev range on the street can be a waste too IMO. How many times to you really get to stretch the zeds legs legally on the street anyway. With all the traffic lights and stop signs and roundabouts around it stop start city out there. My point being these cars are still a three litre V6 and without turbos they are still a quick car and will hold there own against most so I personally dont mind a laggier car i.e a car that may start spooling higher in the rev range and develop peak boost higher up too. My car currently develops peak power at around 5600 rpm ad nthe lower curve kicks off around 3200 rpm its a steep curve to 5600 when she is hitting 270 odd and you feel it on the street. Its an interesting topic and good to see peoples different views on whats laggy and whats not.
lag on the street really shouldnt be an issue in my opinion. When you are on the street and want to strectch the zeds legs you will go through 1st and second before braking the speed limit and you would still doing it illigally as u are wheel spinning and fishtailing all over the place. my point trying to be that, if you are goin to strectch the zeds legs on the street you are going to be doing it illigally even with standard turbos and lag so why not go all out. having lag at 4500rpm would be awesome But if you have this kind of lag/power why would you even bother racing on the streets, there would pretty much be no competition. let alone the major traction issues you would have with street legal tyres. I reckon the tt has enought torque off boost to get you from a to b and if you want to stretch the legs of the zed why not have it come on at 4500. just my 2 cents
I'm not sure I understand. I believe Lag is a big issue on a street car because of the simple fact that 90% of the time (well maybe not for Zed owners ) you're not on boost. Most of the time the car is running below 3,500 rpm (2,000-2,500rpm while cruising), which means if you need power really quick (to overtake) you have to wait for the turbos to spool up (lag), or gear down but that too takes some time for the turbo to spool up. Like I said I never noticed the lag to be an issue until I drove the VW. As you guys have pointed out once you've hitting the real boost in our cars you're probably already breaking the speed limit, so I'd like to have the boost come on earlier.
Your sort of there Z-ster. Turbos start to spool based on the overall size of the turbo and also how much exhaust flow they are getting to spin the turbines up and create boost on the intake side. How long it takes for this to happen is dependant on the rpm and your setup overall. Most turbos even stock wont reach full boost until quite high in the rev range anyway and nearly all charts I have seen develop peak power right up the rev range my car is 6000 rpm roughly. Boost may come on but you will not develop peak power low in the rev range as you suggest. I think the real terms of boost Lag and spool refer to points on the dyno chart. My chart for instance max boost set at 15psi power run 4th gear 25 degree ambient temp. Boost starts to build from 2500 rpm car is making 80 odd rwkw at 5psi. At 10psi 2800rpm makes 120rwkw At 15psi 3300 rpm makes 160 rwkw then from that point through to 6000 rpm power builds from 160rwkw to a max of 248.3rwkw over the space of 2700rpm which I think they call the power band of the setup where the turbo is creating max boost and continually building power until it spins to fast and boost drops off the efficiency curve of the turbo itself. So whats Lag and whats Spool or is it the same thing. Spool in the term of the word should refer to the time it takes the turbo to reach its max boost which in my cars case is not long at all so maybe lag is the same its the time it takes the turbo to spool to full boost potential.mmmmmm questions. I know on the track or street for that matter if I drop a gear and the tacho sits above 3500rpm its go go time baby much below that and it does boost but only to the psi shown above. I wonder if the turbos would spool to full boost while cruising at 2500 rpm as you suggest might have to try that tomorrow. Sorry to rave on going now
hmmm, I wonder........ I have been thinking of this for a while but other car makers use a smaller turbo in front of a larger (laggier) turbo to overcome lag. Ie, sequential turbo's. Has this been done in a zed? Is there room? Could you make room? Is it at all feaseable?
