I need more air.........
Le Mans Master
Joined: Apr 2005
Posts: 6,413
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From: The Old Dominion
I just mean you have not yet ruled out the TB or the MAF. Ruling out the air intake tract is easy, just remove it. Ruling out the MAF or TB... Not so easy. If you can find someone with a larger TB who is willing to swap with you so you can do some datalogging, that would seem like a good way to go.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Of course they are. No where near the same size because of the D shape header flange on the LT's. Here is a pic of the exhaust port on the AFR's. As I have said AFR says no problems with running the D port. I guess that means it will run but they don't really say if it would run better with a header with a port better suited for their heads.
AFR exhaust port
Stock LT1 exhaust port
AFR exhaust port
Stock LT1 exhaust port
Last edited by Weav's Vet; Jun 27, 2010 at 10:18 AM.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
That would mean it isn't that the TB isn't opening all the way. It doesn't mean that the TB is not the restriction. I'm not saying it is, I've no idea how to size LT1/4 throttle bodies.
I just mean you have not yet ruled out the TB or the MAF. Ruling out the air intake tract is easy, just remove it. Ruling out the MAF or TB... Not so easy. If you can find someone with a larger TB who is willing to swap with you so you can do some datalogging, that would seem like a good way to go.
I just mean you have not yet ruled out the TB or the MAF. Ruling out the air intake tract is easy, just remove it. Ruling out the MAF or TB... Not so easy. If you can find someone with a larger TB who is willing to swap with you so you can do some datalogging, that would seem like a good way to go.
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
Of course they are. No where near the same size because of the D shape header flange on the LT's. Here is a pic of the exhaust port on the AFR's. I wish I had a pic of the stock ports but I don't. Maybe someone else has a pic so we can compare. As I said AFR says no problems with running the D port. I guess that means it will run but they don't really say if it would run better with a header with a port better suited for their heads.
I had header gasket issue when I changed to the AI 200s my Percy's gaskets were blocking the port a little.....
Finding the right gasket helped end the soft upper end....
IMO if your heads are as good as claimed and you are using the 280XFI your engine should pull up to your redline...
However, lousy exhaust doesn't explain a high map to baro pressure delta..(if in fact you have a high delta)
I remember reading (shortly after the edelbrock manifolds release) that the Edelbrock LT1/4 airgap manifold had a decreased plenum volume....I wonder if the decreased plenum volume has anything to do with your map/baro delta...
Mike
Race Director
Joined: Jun 2009
Posts: 10,428
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From: Southside of Western Norte Americano State of Confusion, ColoFornia
St. Jude '13
If Im translating correctly, what your tuner is telling you into "old guy "terms.. you have more manifold vacuum at a given rpm than he thinks you should (Map low).. while I dont have a lot to offer on the computer stuff as far a figuring out if the reading is correct.. I can add that nothing on the exhaust side of the engine will affect that. that has to be a restriction to airflow on the intake side. from the valves out. and could be a factor of the cam profile, Im not conversant enough to explain it, but there are those on here that can explain how split overlap etc can increase manifold vacuum at all throttle positions. If its tuned correctly (correct AF, Timing at all rpms etc) I wouldnt get too excited about it. every engine is different, and responds differently to mods.
exhaust issues will cost you power,Rpm and throttle response in extreme cases, and Im sure the header flanges blocking those enormous exhaust port is costing you a bit of potential power.
Just a different perspective on it, hope it helps.
exhaust issues will cost you power,Rpm and throttle response in extreme cases, and Im sure the header flanges blocking those enormous exhaust port is costing you a bit of potential power.
Just a different perspective on it, hope it helps.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Of course they are. No where near the same size because of the D shape header flange on the LT's. Here is a pic of the exhaust port on the AFR's. As I have said AFR says no problems with running the D port. I guess that means it will run but they don't really say if it would run better with a header with a port better suited for their heads.
AFR exhaust port
Stock LT1 exhaust port
AFR exhaust port
Stock LT1 exhaust port
I don't think it's obvious that AFR's would/wouldn't be covered better by the SW header's you're running. IIRC, someone else running 1 5/8" round headers on AFR 195's (L98s) said they didn't cover any part of their exhaust ports.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Tell me you placed a header gasket on (both) the heads to see what kind of mismatch you have. Notice the LT1 ports actually LOOK higher in relation to the header bolts than the AFRs. (They look more centered.)
I don't think it's obvious that AFR's would/wouldn't be covered better by the SW header's you're running. IIRC, someone else running 1 5/8" round headers on AFR 195's (L98s) said they didn't cover any part of their exhaust ports.
I don't think it's obvious that AFR's would/wouldn't be covered better by the SW header's you're running. IIRC, someone else running 1 5/8" round headers on AFR 195's (L98s) said they didn't cover any part of their exhaust ports.
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Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
I did kind of rule out the MAF Bob. Yesterdays log was with a different MAF sensor and also the filter removed. Very little if any change was noted. Tuner says a 48 would probably be good enough for my mods. I'm running a 52 at the moment. I do have someone who has offered to loan me a 58. Just seems kind of pointless after what the tuner said.
2. Why does your tuner think a 48 would not introduce some drop in MAP?? I am running a 58......and for max power there is absolultely no logical argument this is not better than a 48 or 52
Does he actually have data from a setup similiar to yours showing less drop in MAP. Bothers me he mentions the value of MAP, not the drop as RPM goes up...
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
1. Was the second MAF different design than the first??? FWIW I have removed the screen on my MAF...no before and after data, but visually it had to help..
2. Why does your tuner think a 48 would not introduce some drop in MAP?? I am running a 58......and for max power there is absolultely no logical argument this is not better than a 48 or 52
Does he actually have data from a setup similiar to yours showing less drop in MAP. Bothers me he mentions the value of MAP, not the drop as RPM goes up...
2. Why does your tuner think a 48 would not introduce some drop in MAP?? I am running a 58......and for max power there is absolultely no logical argument this is not better than a 48 or 52
Does he actually have data from a setup similiar to yours showing less drop in MAP. Bothers me he mentions the value of MAP, not the drop as RPM goes up...
Thanks for chiming in!
The second MAFwas a fairly new Delphi I had. I tried a de screened Grannitelli on it and the car wouldn't hardly run. POS.
I can't answer for my tuner. But I would think he is using settings he knows are from a similar setup as mine for the base tune. Now that the data logging is going on he can adjust or fine tune different settings to max out the motor. I'm going to try a 58mm just to see if it helps. That should narrow things down some.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Thanks for chiming in!
The second MAFwas a fairly new Delphi I had. I tried a de screened Grannitelli on it and the car wouldn't hardly run. POS.
I can't answer for my tuner. But I would think he is using settings he knows are from a similar setup as mine for the base tune. Now that the data logging is going on he can adjust or fine tune different settings to max out the motor. I'm going to try a 58mm just to see if it helps. That should narrow things down some.
The second MAFwas a fairly new Delphi I had. I tried a de screened Grannitelli on it and the car wouldn't hardly run. POS.
I can't answer for my tuner. But I would think he is using settings he knows are from a similar setup as mine for the base tune. Now that the data logging is going on he can adjust or fine tune different settings to max out the motor. I'm going to try a 58mm just to see if it helps. That should narrow things down some.
Removing the MAF screen is relatively easy.....need to remove the inside snap ring and CAREFULLY remove the screen......having said that I did mess mine up a little when I took it out, but I have no plans to reinstall it.
Good Luck!!
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Just confirming when you try the 58mm, be sure it is on a manifold that has 58mm or larger openings.....The new Edelbrock if that is what you are using should be set up with larger openings....I opened up my stock LT4 manifold to match when I went to the 58 TB
Removing the MAF screen is relatively easy.....need to remove the inside snap ring and CAREFULLY remove the screen......having said that I did mess mine up a little when I took it out, but I have no plans to reinstall it.
Good Luck!!
Removing the MAF screen is relatively easy.....need to remove the inside snap ring and CAREFULLY remove the screen......having said that I did mess mine up a little when I took it out, but I have no plans to reinstall it.
Good Luck!!
I had the screen out before but just to clean and inspect it and also to clean the wires with a cuetip and alcohol. I may try running it this time just to see what happens. Thanks again
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Seems like good basic info on this site on a lot of things. It helped me a lot with comprehending all of this stuff a little better.
http://www.injuneer.com/ScanMast.html
http://www.injuneer.com/ScanMast.html