Tuning a speed density system with mods

Fostang · 07-07-2002, 12:27 AM

I'm new to efi systems ever since converting my fastback but since my conversion with MAF didn't work correctly I switched to speed density and it worked better than with MAF. Now my concern is that the mods that I did may cause some problem with speed density. I opened up the TB induction because I'll be putting on a 65 mm tb sooner or later but has a 58 now. The upper and lower were gasket match, the lower was gasket matched to the heads, the exhaust side was ported, long tubes were installed with 1 5/8 primaries no cats with full exhaust is in place, smog equipment was removed. What should I start by checking or playing around with till I get it right? The idle seems to slowly come down after reving it and stays at 1200 rpm then drops to 800 and then back to 1200 rpm after a while then back down. The engine shakes a little but not as bad as when running the MAF. So any tunning ideas? Oh yeah and one last question is the right O2 the drivers side?

Stang Runner · 07-07-2002, 04:29 PM

well it is EZ to tune a SD not to much you can do I am SD still.

Fostang · 07-07-2002, 10:24 PM

What should vacuum be reading right now it reads around 20 hg if I rev it then it moves to 14 hg and then to 24 hg and back down to 20 hg. Also whats a good starting point for the fuel pressure? How about timing?

Old Guy with 87 GT · 07-07-2002, 10:59 PM

i'm still running speed density .........i keep my timing at 15* initial timing and the stock fuel psi seems to work pretty good (39 psi w/vac disconnected)

i'm planing to run it on a dyno in a couple of weeks to see how it's running rich/lean wise........as far as i can tell ,at 39 psi i don't smell it running rich so i think it's pretty close......remind me and i'll let you know how the dyno tinkering does

oh ya ....not sure bout vacuum ,but mine would be different caus of the different intake

Dark_5.0 · 07-09-2002, 07:26 AM

I am still speed density..........Easy money..

Fostang · 07-09-2002, 02:19 PM

Should I get an adjustable fp regulator if I can smell it being a little over rich?

Old Guy with 87 GT · 07-10-2002, 11:32 PM

fostang ......it might be nessesary to get one ........it depends on what your presuse is doing ,get a fuel psi gauge first then run it and see how its doing rich/lean wise and psi wise

although mine is "set" at stock psi ,with the stock regulator my psi would be different ........do to the vacuum levels being different from mods i've done ......thats my theory any way ......i'm not positive cause i got the regulator before i got the different intake ,.....now if i get an aftermarket cam i'm told i will need the regulator ,cams definatly change the vacuum levels too much for the stock regulator to function properly

btw .....i unhook the vacuum line to set at 39 psi then hook it back up .......with vac line hooked up and at idle it stays around 31-32 psi

also.....it'll probly be a while till i get the dyno tune ,unexpected financial problems ......me's to broke to get it tuned right

07-07-2002, 12:27 AM	#1
Fostang Registered Member Join Date: Feb 2001 Location: Stockton, Ca Posts: 599	Tuning a speed density system with mods I'm new to efi systems ever since converting my fastback but since my conversion with MAF didn't work correctly I switched to speed density and it worked better than with MAF. Now my concern is that the mods that I did may cause some problem with speed density. I opened up the TB induction because I'll be putting on a 65 mm tb sooner or later but has a 58 now. The upper and lower were gasket match, the lower was gasket matched to the heads, the exhaust side was ported, long tubes were installed with 1 5/8 primaries no cats with full exhaust is in place, smog equipment was removed. What should I start by checking or playing around with till I get it right? The idle seems to slowly come down after reving it and stays at 1200 rpm then drops to 800 and then back to 1200 rpm after a while then back down. The engine shakes a little but not as bad as when running the MAF. So any tunning ideas? Oh yeah and one last question is the right O2 the drivers side? __________________ 67' Fastback-Supercharged 4.6 DOHC Cobra, T-56, 8.8 more to come. 67' Coupe-EFI, AOD, 8.8 90 Gt-Supercharged,MAF,TB,1.7's ripper, bassani x, 3.55's, 01' cobras, headers. 89'GT-Supercharged,Heads,Cam,Intake,TB,MAF,power pipe,headers,offroad exhaust,black bullits.

07-07-2002, 04:29 PM	#2
Stang Runner Registered Member Join Date: Jun 1999 Location: Walker, MI, USA Posts: 1,202	well it is EZ to tune a SD not to much you can do I am SD still. __________________ Engine: steel mounts, Under drive pulleys, K&N, GT-40 Intake ported Lower, No power steering, No A/C, Mac cold intake, 65MM TB, 255 Fuel pump, 24's, AFR 165 58cc, Rocker Arms 1.7with the stock Cam, 1 5/8 short headers, offRoad X-pipe Drive Train: 3.55, T-5 with a Pro 5.0 shifter 12.656@107.71MPH See It at www.T-racing.com/mustang.htm

07-07-2002, 10:24 PM	#3
Fostang Registered Member Join Date: Feb 2001 Location: Stockton, Ca Posts: 599	What should vacuum be reading right now it reads around 20 hg if I rev it then it moves to 14 hg and then to 24 hg and back down to 20 hg. Also whats a good starting point for the fuel pressure? How about timing? __________________ 67' Fastback-Supercharged 4.6 DOHC Cobra, T-56, 8.8 more to come. 67' Coupe-EFI, AOD, 8.8 90 Gt-Supercharged,MAF,TB,1.7's ripper, bassani x, 3.55's, 01' cobras, headers. 89'GT-Supercharged,Heads,Cam,Intake,TB,MAF,power pipe,headers,offroad exhaust,black bullits.

07-07-2002, 10:59 PM	#4
Old Guy with 87 GT Registered Member Join Date: May 2001 Location: Harrisburg, Pennsylvania Posts: 379	i'm still running speed density .........i keep my timing at 15* initial timing and the stock fuel psi seems to work pretty good (39 psi w/vac disconnected) i'm planing to run it on a dyno in a couple of weeks to see how it's running rich/lean wise........as far as i can tell ,at 39 psi i don't smell it running rich so i think it's pretty close......remind me and i'll let you know how the dyno tinkering does oh ya ....not sure bout vacuum ,but mine would be different caus of the different intake __________________ the "not so old",old guy 87 Mustang GT T-top >hanlon t-5, pro 5.0, centerforce clutch ,adj. cable/quatrant ,3.27s ,full 2 1/2 ex(off road H) adj. reg. ,e-cam ,70mm TB, cobra intake ,1.7rr ,ported/milled e7ets w/crane springs ,306 balaced/decked short block w/speed pro forged flat top pistons ...257rwhp/302rwt best et 13.7@102 (4/11 ) '80 Capri (future project,currently collecting parts for 351 moter)

07-09-2002, 07:26 AM	#5
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	I am still speed density..........Easy money.. __________________ 92' LX-Big brakes, Lots and lots of suspension, GT40X heads, Ported cobra intake, stock cam, Vortech SC trim. 00' Lightning-Stock 88'CRX-13 second ego killer

07-09-2002, 02:19 PM	#6
Fostang Registered Member Join Date: Feb 2001 Location: Stockton, Ca Posts: 599	Should I get an adjustable fp regulator if I can smell it being a little over rich? __________________ 67' Fastback-Supercharged 4.6 DOHC Cobra, T-56, 8.8 more to come. 67' Coupe-EFI, AOD, 8.8 90 Gt-Supercharged,MAF,TB,1.7's ripper, bassani x, 3.55's, 01' cobras, headers. 89'GT-Supercharged,Heads,Cam,Intake,TB,MAF,power pipe,headers,offroad exhaust,black bullits.

07-10-2002, 11:32 PM	#7
Old Guy with 87 GT Registered Member Join Date: May 2001 Location: Harrisburg, Pennsylvania Posts: 379	fostang ......it might be nessesary to get one ........it depends on what your presuse is doing ,get a fuel psi gauge first then run it and see how its doing rich/lean wise and psi wise although mine is "set" at stock psi ,with the stock regulator my psi would be different ........do to the vacuum levels being different from mods i've done ......thats my theory any way ......i'm not positive cause i got the regulator before i got the different intake ,.....now if i get an aftermarket cam i'm told i will need the regulator ,cams definatly change the vacuum levels too much for the stock regulator to function properly btw .....i unhook the vacuum line to set at 39 psi then hook it back up .......with vac line hooked up and at idle it stays around 31-32 psi also.....it'll probly be a while till i get the dyno tune ,unexpected financial problems ......me's to broke to get it tuned right __________________ the "not so old",old guy 87 Mustang GT T-top >hanlon t-5, pro 5.0, centerforce clutch ,adj. cable/quatrant ,3.27s ,full 2 1/2 ex(off road H) adj. reg. ,e-cam ,70mm TB, cobra intake ,1.7rr ,ported/milled e7ets w/crane springs ,306 balaced/decked short block w/speed pro forged flat top pistons ...257rwhp/302rwt best et 13.7@102 (4/11 ) '80 Capri (future project,currently collecting parts for 351 moter)

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