Ok stats first....

Ellis and I just completed my 401ci, 237I/245E .608/.613, 12.5 to 1 comp, AFR 210 heads ported by Lloyd to 290@.600.

Must of you know Ellis has been working on a Lt1/Lt4 manifold that will be raised, but use the same stock fuel rails. He completed it, and we have been tuning the combo ever sense.

The engine shows 101KPA all the way up to 7100 Rpm. The MAF has hit the high limit of 10k something in second gear setting the high MAF freq code...(which we just turned off). I'm assuming it's making good power becuase of hitting the Maf limit, and we have not Wide Band tuned the car yet....

My questions...Does the High 101 KPA from 4100 rpm to 7100 rpm mean the combo is optimized with the ported/welded and raised intake or is the airflow to low through the heads/cam which is causing such a high KPA reading.......I would have thought with this combo the manifold would show some loss....say mid 95 kpa...thought is might have been compression..then thought better....

Jim

 

Compression should not increase flow at a given rpm, it will however help it hold a smoother idle and increase flow at idle but it will do that by increasing average rpm at idle.

 

Yeah, I thought about it a little and when I was typing it dawned on me, the points you listed.....Thanks.....Still odd to see high KPA on a 401...I would have thought there would be some drop with the cubes, cam and rpm...Maybe the intake manifold is just kicking ***!!!!

 

What's the barometric pressure when you are seeing 101kPa MAP?

 

BP, I believe that day was in the low 29.9ish range (just glanced at the news)...
Temp was 50ish degrees
Humidity was probably in the range of 85-90% raining (off and on)...

Our da's usually run in the 1000 to 2000 foot range this time of year if correcting for STD..If using SAE type numbers probably 0 feet....

 

Your scanner should be able to show you barometric pressure, in kPa. That's what you compare the MAP to, top determine the pressure loss in the intake system. Sounds like your sensor may be reading the pressure incorrectly, or you were running it under a very high barometer. Are the readings at other than WOT consistant with the cam you have in the engine?

 

I was using the MAP sensor to get the 101KPA WOT....I guess I'm not getting what your saying....If the Map max number the computer uses is 101 then, if I have the engine off and the key on I should still see 101. If the BP outside was less than the max sensor number I would be able to get a better reading say 95 or 100 kpa. I could then use that number against the WOT KPA number...sound right? But, sense the damn sensor is maxed at WOT, I really don't know what the max BP outside is or the max KPA the engine was pulling...old combo pulled 95 KPA for reference, but I never checked the KPA with engine off....

At idle in gear I get 66 KPA (I believe this is in the 10 inch vacuum range), sounds right for the cam size/lsa, compression and cubic inches...56 KPA in neutral....The only thing that really leads me to believe it's pulling good airflow is the MAF freq maxing out at 7100 in second, I would guess that it would max at 6800ish area in 3rd gear. My old combo 396, decent heads, with GM 847 cam and 10.7 compression never came close to maxing the MAF and made 400rwhp corked up through a 12 bolt stalled auto...

 

When you turn the key on, and don't start the engine, the MAP sensor will tell you the baromeric pressure. I think a 1bar MAP sensor can indicate at least 103kPa. The stock PCM stores that number, and you can read it with a scanner. The ScanMaster, for example, shows that when you set the display to "BAR".

What do you have in front of the throttle body in the way of a filter and ducting? How big is the throttle body? Is the seal on the MAP sensor in good condition?

What exactly does the MAF sensor read when its max'd out? The stock calibration table shows 471 GPS when the MAF frequency is 11,216Hz. Just playing with numbers, a 401ci at 7,000rpm, with a VE of 100% would be consuming 450 GPS of air.

 

Yeah, I'll check the key on BP, but I'm thinking it might only be 101 on this 96 computer I'm using...

The MAP sensor is in good condition and as far as I can tell and the reading look good when giving throttle to idle, to WOT. We use a good rubber hose off the side of the manifold with clamps. Intake is fully ported/welded all the raised bumps inside are gone and all internal surfaces are hard rolled. It's also been cut and raised 3 inches so no room for sensor on top anymore...58mm t-body, maf descreened and Honker (Moroso) air tube....

By Tech 3 it shows 434 GPS (in second gear) at somewhere between 6700 and 7000 and hits the Maf high freq at 7100ish rpm....I swear though the high freq was at 10600ish, maybe that's why we hit it. We turned off the code and raised the freq....I'm thinking that the 3rd gear pulls will bring in another 15 to 20 grams? Plus we still have not tried the cutout...I wish that these numbers are good, but who knows with this stuff......Hopefully the manifold is working that good.......as you can tell though I'm not a trusting soul when it comes to LT1 horse power....

Thanks for the ideas, any more, hit me with them...

Oh yeah, here is short video of car before full exhaust...You can see the manifold work if you stop vid at end....
http://video.ls1tech.com/player.aspx...9-F6CA12E18934

 

Well instead of trying to figure out horse power from "GPS." I went to the dyno today....

448 SAE Rwhp/424 SAE Rwtq
The engine only has 300 or so miles, I'm hoping we can see another 10 more hp when the rings loosin up abit....

401
4l60E
Pi 3200 (4100 stall)
12 bolt 3.73 gear

Here is some vids of car running from 3800 to 7100rpms
http://www.highspeedproducts.com/video/Jimbo.wmv

Jim

 

Nice #'s, is that amount of smoke out the exhaust normal? Or do the rings still have to wear in a little?

 

Normal...Actually, there was very little smoke you could see, the camera overemphasized the amount, and yes it only has 300 miles on engine....

 

Just an update on KPA...

We did finally see some loss through system...Now I feel better...Thought my heads/cam were not pulling enough....At 101 KPA (key off), we saw 96 KPA at 7000 RPM....I'm guessing that in second gear (on road) we could not get enough (pull), airflow. Now after dynoing it in 3rd we were able to see the real results (or closer to it)....

Sound like a reasonable assumption ?