K series lost power?

[p.mole1]

If I am using solid tappets do I have to take into account the valve clearances when setting the cam timing? I used SuperSport cams and the recommended timing figures are 80 thou inlet  and 60/65 thou exhaust.( with throttle bodies). Should I have deducted the valve clearance 80 - 8 and set the timing to 72 thou. Have I over advanced my timing and killed all the top end power? seems I am .5 bhp down on standard. Are the standard 1.4 Supersport injectors running close their maximum output in standard form. I must say I was a tad disappointed I was expecting around 140 bhp. 

I also noticed my transmission losses were quite bad I ended up with 100 bhp at the wheels. I was almost managing that output  with A series Minis! 25 years ago

[oilyhands]

No, just set the lift at TDC from the latent position of the follower, ignore the clearance.

The 1400 SS engines dont make the claimed power.

At that spec I would expect you to make around 100-105BHP per litre. 

Oily

[p.mole1]

It seems like the transmission loss is about right, 

RWD cars - add 10 to the wheel bhp and then divide the result by 0.88 i know its a rough estimate that gives about 125 flywheel bhp. 

[p.mole1]

Thanks oilyhands that's about what I was expecting,John Sleath does not have a reputation for over inflating dyno readings and outputs,he had some impressive V8 stuff in his workshop and has a 1000 bhp Ultima!  which he inherited and detuned to 500 bhp to make it more usable. I suppose when you can dyno cars with over 1500 bhp at the wheels! a lower reading makes no difference whatsoever. The car feels much quicker but now I've convinced myself its not (probably a placebo effect) however if my injectors are close to limit I must be producing more power unless the standard injectors were already at the state in standard form.

Just to convince myself everything is ok I will do a compression test and may order a cheap cylinder leak down tester from China

[p.mole1]

I have been looking at injectors and it seems I should have used a higher rated one.

Looking at the rough calculation of injector sizing 149cc/minute x 4 divide by 5 gives the rough maximum hp output at 100% duty cycle at 3 bar fuel pressure.

So with that calculation it gives me a maximum rating of of 119 bhp or 95 bhp at an 80% duty cycle I'm assuming these calculations are erring on the side of caution. If this is the case the Supersports rated power output seems wildly optimistic unless it is using a higher rated fuel pressure regulator.

I don't know if this calculation is the same or even correct for both batch fired and sequential injectors, I should have done my homework before I started, never had any of these problems with carbs

[revilla]

Surely though if they were able to maintain a sensible AFR right up to the RPM limit at WOT the injectors must be coping, i.e. being able to deliver the appropriate quantity of fuel for the air flow achieved, even if they are getting close to their limit? If so I don't see how bigger injectors will deliver more power, they will just end up running a lower duty cycle with a bit more spare capacity. That is according to my simplistic thinking - happy to be corrected though.

[p.mole1]

I'm assuming my injectors are at the absolute maximum if my calculations are correct that's not a very good idea they should be around 80 to 90%. I came away from the rolling road with 127.5 bhp after fitting a Janspeed ported head with 11-1 compression ratio, 4-2-1 exhaust,verniers,42 mm Jenvey DTH 90mm bell mouths and an Autotechnics air box and a heat shield to keep the hot air from the radiator away to an otherwise std 1.4ss. In standard form a SS should make 128 bhp, but it's injectors don't appear to be large enough unless it has higher fuel pressure. Assuming Caterhams power ouput claims are 10% optimistic that would give a realistic output of 115 bhp.

I seem to have gone to all this effort just to get to the manufactures claimed output,not really very impressive,it works out at about 90 bhp per liter, I was expecting a bit better than that,embarrassingly my friends 1430cc  A series Mini nearly matches that on a single SU carburetor and a distributor! measured at Aldons

Looking at the dyno graph the power seems quite linear and is peaking at about 7500 and not really falling of at the limiter so I don't think there is anything wrong with my cam timing

Fitting larger injectors wouldn't of made any difference to the power output it would stop them running close to maximum.

[p.mole1]

Have been doing some homework

Looks like 127.5 bhp is about spot on  if the formula is correct

Known Hp x Brake specific fuel consumption     equals fuel used in lbs/hr

Number of injectors x duty cycle

127.5 x .42 ( I think this is the correct figure)                                                                                                                                                    

 14.09 x 10.5 to convert to cc/min 

4 x 95%

I get an injector flow of 148 cc/min 

Math's is not my strong point, but if the formula are correct, (probably an over-simplification)  it looks like achieving 100 Bhp per litre is going to be a lot harder than I thought. I think my exhaust primaries are probably to large, and the throttle bodies are a tad to big for a 1.4? also maybe the  intake trumpets could be to long? Since the valves are the maximum size the only way to achieve the goal would be more lift and a lot more revs. So after all that I'm .5 bhp down! Have double checked everything and I'm getting full throttle, I will do a compression test however the valves and seats  looked brand new

[p.mole1]

I'm getting a bit worried about taking my car on a trackday with my injectors working flat out,it won't take much to go lean at full throttle ie a slight dop in fuel pressure and pistons will let go. How difficult is it to re-scale larger injectors and how accurate is it, as regards getting the fueling correct. Dave Andrews kindly sent me a 1.6 re-scaled map just so I could get the car running but is was very rich at part throttle because it was a best guess. Now I have a the fueling set up is there a method of calculating the % figures  or will I have to back to a rolling road?.

[p.mole1]

I have found and injector table ( Stan Weiss efi flow data table ) 

The black injectors 176cc/min give  122 hp est at 95% duty cycle at 3 bar

The cream injectors 218cc/min give  152 hp est at 95% duty cycle no fuel pressure shown

All these figures seem very low since its not recommended to run injectors at these duty cycles,am I missing something or is everybody running higher fuel pressures to compensate for the low flow rates on these injectors. Are the quoted Rover power outputs accurate ?

[revilla]

I'm as confused as you are on this. I've looked into this before. My engine is a VVC 160, and they certainly can make rated power of 160 bhp in a Caterham. Assuming I want no more than 85% duty cycle I reckon the injectors would need to flow in the region of 220-230 cc/min, but the standard blue injectors for this engine are rated at 191.8cc/min. With a Kmaps remap the engines can make up to 175 bhp and still run the standard injectors at the standard 3 bar quite happily. I have no evidence to suggest detonation and when I've stripped my engines the plugs and pistons have always looked perfectly healthy. So how come all the standard calculations for injector sizing suggest that our injectors are undersized / overworked but they still run with no problems? I would also love to understand if anyone can please explain?

[Rob Walker]

Sorry to be the bearer of bad news but your cams are too mild to make any substantial use of the upgraded throttle body injection.  Suggest you fit some BP285M or hotter .

[p.mole1]

Thanks Revilla it is quite confusing I can only assume the injector flow charts are a guide and they are capable of flowing more that stated. I certainly hope that is the case. I am assuming the rolling road is reading low. It seems strange that the 1.4 Super sport has an a 149cc/ min injector that is rated to give 103.5 hp at 95% duty cycle on an engine that is supposed to develop 128 hp 

[p.mole1]

Hi Rob I know I am running quite mild cams, I intend to build a 1.6 in the future ( all the stuff is transferable) so I wasn't really expecting any real gains from the throttle bodies, but I was expecting something from the cylinder head and the K6. I am limited by the pistons I can't fit any wilder cams,as it is the power looks like its still useable to 8000rpm and I suspect maximum power on a 1.4 will be above this figure also I can only use solid tappets which mean using the 285 solid version which is more aggressive

One thing I have gained is a massive boost in the midrange or at least that's what it feels like driving it. I'm off into the garage to do a compression test.

[revilla]

The original post in this thread:http://forums.mg-rover.org/mg-zr-rover-25-200-streetwise-101/limits-injectors-throttle-805890/#/topics/805890?page=1 (sorry can't do a link as I'm on my phone) seems to suggest that he had the flow rate of the VVC injectors measured when they vere serviced and they came out 10% higher than the quoted figures. I'm also wondering if (and I'm out of my depth here so it is just educated guesswork) the typical Brake Specific Fuel Consumption figures quoted and used in the flow rate calculations may be a bit on the high side for a high revving, reasonably high compression and clean burning engine like a K Series? A lot of the websites that will calculate injector sizes for you seem to use the same figures for American V8s. I think I saw a BSFC figure of 0.42 in a paper for a 1.4K somewhere but can't find the reference now. I know when they went from EU2 to EU3 on the VVC and increased from 143bp to 160bhp they actually REDUCED the injector flow rate - my guess is that this was purely for emissions and a smaller injector may have given a better spray pattern and atomisation; buy it would suggest that they were looking to size the injectors "just big enough" without much margin for error.

[p.mole1]

Hi Revilla thanks for the input,that's an interesting article. I have just completed a compression check and all is fine,in fact couldn't be better 

1 220 psi

2 220 psi

3 215 psi

4 220 psi

I have never had an engine with such a consistent reading.

If my injectors are able to flow 10% more than standard this give me around 140 hp which is what I was expecting.  I will get my injectors flow tested,that's the only way I will know with any certainty 

 

[oilyhands]

The SS cams are capable of producing good output on TBs, the best I have seen on a 1600 with SS cams , TBs and ported head is over 180 BHP. 

Oily

[AlexanderJ]

how close are you to Northampton Motor Sport ?

[p.mole1]

Hi Alexander I'm in the very north. Not much up here! I will at some stage remove my injectors and get them flow tested and I should really measure my fuel pressure, that should give me a reasonable idea.