Stay with FI, or go to Carbs?

Road-race engines and ancillaries - general discussion
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vandor
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Re: Stay with FI, or go to Carbs?

Post by vandor » February 23rd, 2011, 6:31 am

Guy,

I spent a few hours disassembling and measuring things, and now I have the cam lift vs crank position data.
It's 64 data points, it would be hard to decipher here, should I just email it to you?
Thanks,

Csaba
GC book #288

Guy Croft
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Re: Stay with FI, or go to Carbs?

Post by Guy Croft » February 23rd, 2011, 10:02 am

Sure, mail it.

G

vandor
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Re: Stay with FI, or go to Carbs?

Post by vandor » February 25th, 2011, 2:51 am

Guy,

Did you get my email? I sent it Wednesday morning.
Thanks,

Csaba
GC book #288

ace124
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Re: Stay with FI, or go to Carbs?

Post by ace124 » February 25th, 2011, 4:51 am

For those of us following this thread can you plz post the cam graph.

vandor
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Re: Stay with FI, or go to Carbs?

Post by vandor » February 25th, 2011, 6:13 am

Hi,

I don't know how to export a graph from Excel, so here is a pic I took of my screen. Y-axis is cam lift in inches, X is crank (not cam) rotation in degrees.

Csaba
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4282profile.JPG
42/82 cam profile
4282profile.JPG (111.37 KiB) Viewed 3017 times
GC book #288

Guy Croft
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Re: Stay with FI, or go to Carbs?

Post by Guy Croft » February 25th, 2011, 11:28 am

To present Excel as a picture you copy and paste into MS Paint and save as a JPEG.

However you may not need to now. I have done some work on this as best I can. For the record you should always present cam data by cam degrees of rotation not crank and you should do it at 1 degree rotation. What cam mfr do is another matter, this for our purposes here.

So I have 'rejigged' your data and matched it (again - as best I can) against two other profiles, the old Alquati billet 77 profile and a billet GC 3A. Robert has already remarked how he compared the 3A against the same cam you have and the graph seems to say the same thing. The astute reader will ask whether my maps factor in valve clearance as of course Csaba's data does (taken as it is off-engine) and the answer is no my data is zero clearance flat-follower lift straight off the cam - Csaba's is valve lift with real-world running clearance.

Unwise for me to be too clever about this without the full cam map and I don't want to give the impression of vendor bashing but a glance at the relative areas under the curves (which are presented from full lift to closure) pretty well says it all.

GC
Attachments
GC_77_CV cams.JPG
CV is Csaba Vandor's cam
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vandor
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Re: Stay with FI, or go to Carbs?

Post by vandor » February 25th, 2011, 4:22 pm

Well, holy son of camshaft! That would probably explain the lack of top end power.
The interesting thing is that the Alquati '77' profile is what is also known as the '40-80' profile, and it's supposed to be milder than what we have.
So we need different cams. Based on this info I think the idle problem is not related to the current cams, but likely to the individual runner setup.
I need to talk to Jeff, the car owner, and we need to make some decisions.

Thanks Guy!

Csaba
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Guy Croft
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Re: Stay with FI, or go to Carbs?

Post by Guy Croft » February 25th, 2011, 4:44 pm

yes buy some 3A's

GC

Guy Croft
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Re: Stay with FI, or go to Carbs?

Post by Guy Croft » February 25th, 2011, 5:13 pm

I might venture to suggest that your billet grind has - maybe - at some point actually been 'mastered' off a regrind. If that is the case IAP (as they are now) may not know that.I may be wrong but based on the lift degree data you gave me it looks a very weak billet profile for a billet. That would explain everything because a regrind would give you precisely what you've got. You might get away with it in a 1438TC maybe but no way in a 2 liter.

G

engineerted
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Re: Stay with FI, or go to Carbs?

Post by engineerted » February 25th, 2011, 10:47 pm

I don't know if that totally explains the top end power but it looks to be a good start. Now I am going to have to measure up my IAP cam (42/82) from the race car and see how it compares to the other billet (40/80) cam that I have in my street spider. Please note that I do not have the same issues Csaba is having but I am curious to see how they compare to each other and I have a sneaky feeling that even though the total lift may be greater with the 42/82's , the area under the curve for the 40/80's may be larger. ?? I will report back when I get some results.

Edited is thread, It looks like the 40/80 cams that I have in the street spider may not be what I thought they where. The data seems to indicate that they are Pittore 87 grind. The only marking on the cam is 87 stamped on the end. Guy I sent you the data, any thoughts? Maybe I should move this to a new thread?

Ted
74FP SCCA 124 spider

vandor
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Re: Stay with FI, or go to Carbs?

Post by vandor » February 26th, 2011, 7:14 pm

Ted,

AFAIK the '87' grind is 42/82. However, at this point all cams are suspect :-)

We decided to go with the Croft 3A cams, and dyno the car with the current FI system. However, we are almost certain that this FI system will not be able to
give good idle and driveability.
The big question then is to go to dual IDFs (40s or 44s?), or a more tuneable fuel injection system (Haltech?)? The IDFs would take a lot less time and dyno
time to tune.
I know there is no 'proper' manifold for the 44s, so we'd need to port the one made for 40s (we have one from Pierce Manifolds). Any other mods the 44 IDFs
need?
Thanks,

Csaba
GC book #288

dp
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Re: Stay with FI, or go to Carbs?

Post by dp » February 26th, 2011, 9:01 pm

Guy Croft wrote:To present Excel as a picture you copy and paste into MS Paint and save as a JPEG.
[EDIT]

GC
A quick and dirty way to capture an image from almost any program on a PC is to get the required image taking up as much of the screen as possible, pressing the "Print Screen" key (maybe PRT SCR) to the right of the F12 key then opening MS Paint and pasting as above.

You will have made a picture of your whole screen from which you can crop out the extraneous stuff around the edges.

robert kenney
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Re: Stay with FI, or go to Carbs?

Post by robert kenney » February 26th, 2011, 10:10 pm

Csaba,
I would not move away from your existing EFI system. No reason it would not take a tune that would run properly. At least untill you have had a chance to install the new cams and tweak on the EFI some more.


How well matched are the throttle bodies? Any differance in flow will kill the idle quality. Do you have any ports down stream of the throttle plates that you can T together? A quick 1/4" vacuum hose and T arrangment can be assembled in short order. This will help eliminate any small flow variations between cylinders at idle.

Header temps are going to be key here also. Do you have a IR thermometer? Don't rely on the AFR gauge at idle. Large cams idle so dirty that you will not have reliable readings. The fact that you are running batch fired injectors suggests to me you could have cylinders that are not carrying their share of the work. Some lean some rich.
Robert Kenney # 111

kpsig
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Re: Stay with FI, or go to Carbs?

Post by kpsig » February 27th, 2011, 10:31 am

I agree with Robert except to the point of batched firing sequence of the injectors.
This is not a reason for erratic idle, acceleration or loss of power, out of my experience. Its only drawbacks are somehow higher emissions and slightly more fuel consumption.
Kostas, Greece

robert kenney
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Re: Stay with FI, or go to Carbs?

Post by robert kenney » February 27th, 2011, 3:10 pm

kpsig wrote:I agree with Robert except to the point of batched firing sequence of the injectors.
This is not a reason for erratic idle, acceleration or loss of power, out of my experience. Its only drawbacks are somehow higher emissions and slightly more fuel consumption.
I think you miss understood by point regarding batch fired injection. 99% of aftermarket EFI systems are 1 or 2 channel. They work very well on common plenum induction systems because of balances air flow at idle. This is where the batch firing and discrete runner induction leaves much to be desired. With this EFI injector firing all as one one can not compensate for individual cylinder flow unbalance. My compromise approach is a port balancing apparatus hence the vacuum line T situation.

Make absolute certain the cylinders are balanced. Make sure the idle fuel map is correct and 10% on the rich side. Most of these setups will perform better from a drivebility stand point slightly rich of peak at low speed. Give the engine more throttle opening to acheive proper idle speed.

If it still will not behave make sure the system is realy open loop. Make sure the sensor grounds are properly bonded and that you don't have feed back issues.

If you loose a coolant of inlet air sensor the systen should have a default base setting is can use and still run.Can you remove one at a time ans see if it helps. I see no reason the fuel map should be moving like it is.

Are you using a MAP corrected fuel pressure regulator? Can you lower the pressure?

I watched video 1 again and the surge seems to corelate to the injector duty cycle swinging between 4% and 5%. That may be huge at idle. Is there any way to alter the injector gain? What is causing the duty % to swing? If the TPS and rpm range is constant the duty % should remain constant in open loop.
Robert Kenney # 111

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