Dyno Tune

[yabadaba]

Hi guys, as per one of my other threads I've pretty much decided on long tube headers with a catted y-pipe as my first significant mod. But, from what I've picked up over on some of the yank forums it looks like I won't reap all the benefits without having a tune performed after the install.

Does anyone know where I can get a dyno tune done on my 2001 z28?

Btw, got my GMMG catback fitted today....sounds amazing...turned the stereo off for the drive home as I had something far sweeter to listen to

[ringram]

RapidGb should be able to sort you out. Or you could roll your own tune with efilive or similar.

[yabadaba]

Thanks...just found the RapidGB website....looks like they know their way around the LSx series of engines.

I've actually got HPTuners but haven't learned how to use it yet and I think I'd need a wideband meter anyway to do a tune properly, so better leave things to the experts to begin with.

[300bhp/ton]

A tune will certainly benefit you. But I'm not sure how much of a gain you are likely to see.

On all the reading I've done, most say don't worry about a tune until you change the cam (or have a specific need, nitrous or FI).

If you have the money spare, or think it's running too rich/lean then go for it.

Will certainly be interested in any results you may get. Would be good if you could get a base line before tuning and one after to see the gains.

Hope it goes well

BTW - what LT's did you go for?

[yabadaba]

Hi 300bhp/ton, good to hear from you. I've not ordered the headers yet, probably in a couple of months time, but have narrowed it down to either Kooks or American Racing. I suspect I'll go with the latter as they do a package that includes a matching catted Y-pipe and from what I've heard (and as you would expect) the two fit together very well and the whole setup doesn't hang too low (loads of speed humps where I live).

I think you're spot on regarding having a dyno to set a baseline before the install . I'm going to give those dyno guys a ring and get myself booked in. Will be intersting to see what the BHP/Torque is like now and just how much difference the headers make. From what I've heard (and I'm sure you mentioned this too) the LS1's respond well to this type of mod.

What I can't make out at present and am reading up on is what effect there might be on low end torque. I've heard some stories about that suffering with a header install. Also, and quite possibly linked to this, I'm not sure whether to go with the 1 3/4" or 1 7/8" diameter versions. I think the smaller diameter ones are generally recommended for anything below 400-500BHP, but there is a post on ls1tech at present (Gen III Ext Engine sub-forum) that seems to question that thinking.

I'll certainly keep you informed.

Edited by yabadaba on Monday 8th September 13:15

[300bhp/ton]

yabadaba said:

Hi 300bhp/ton, good to hear from you. I've not ordered the headers yet, probably in a couple of months time, but have narrowed it down to either Kooks or American Racing. I suspect I'll go with the latter as they do a package that includes a matching catted Y-pipe and from what I've heard (and as you would expect) the two fit together very well and the whole setup doesn't hang too low (loads of speed humps where I live).

I think you're spot on regarding having a dyno to set a baseline before the install . I'm going to give those dyno guys a ring and get myself booked in. Will be intersting to see what the BHP/Torque is like now and just how much difference the headers make. From what I've heard (and I'm sure you mentioned this too) the LS1's respond well to this type of mod.

What I can't make out at present and am reading up on is what effect there might be on low end torque. I've heard some stories about that suffering with a header install. Also, and quite possibly linked to this, I'm not sure whether to go with the 1 3/4" or 1 7/8" diameter versions. I think the smaller diameter ones are generally recommended for anything below 400-500BHP, but there is a post on ls1tech at present (Gen III Ext Engine sub-forum) that seems to question that thinking.

I'll certainly keep you informed.

Edited by yabadaba on Monday 8th September 13:15

Hi.

Regarding losing low end torque, I feel this is something that is often thrown around on forums.

My understanding of it is this.

If you imagine the torque curve as dome shape (actually the LS1 is nearly flat, but ignore this for the present).

Adding LT's reduces back pressure, with correct fuelling (i.e. a tune) you will see more power.

Getting more power means one of two things, or maybe both.

HP = torque x rpm / 5252

So the more torque we make, the more HP. Or make the same torque at higher rpms you will also make more HP.

LT's won't extend the rpm range you're engine makes power at, it simply moves it up the rpms a tad.

e.g.

If in stock trim your toque band is 1500rpm to 4400rpm PEAK.

LT's won't make this any bigger but should move it up the rpms to maybe 1800 to 4800rpm.

(Ignore the numbers as they are for example only)

So in some ways you will get the feeling of less low end power, but you'll get a lot more only slightly higher in the rpms.

Another thing to consider is the feel, adding LT's will make more PEAK HP, so the difference between the low end rpms and the high rpms will be more noticeable. Often giving the impression of less low end torque.


In short, I personally don't feel it is an issue. LT's are a positive mod and one that is recommended.

As to the primaries - well if you plan on over 500bhp then go for the biggest.

Apart from that I personally don't feel there is much of an issue on which you go for. Both will work and work well. Any difference will not be by any huge amount.

In a race car I can it being important, but in a street car less so.


As an example of losing low end torque:

I've got a TR7 V8, ok it's a 3.5 Rover V8, but it has large bore primaries and a 3" Y pipe exhaust setup.

On the stock cam it felt very torquey, but that's because it ran out of breath at about 3000/3500rpm and took an age to wind out past 5000rpm.

After swapping on a new intake manifold, big 4 barrel carb and a high lift cam it was a totally different engine to drive.

It basically gives you kick in the back at 3500rpm now. And loves to rev. By comparison it feels not so torquey. However I'm a strong believer that this is mostly due to the stark black and white difference in the higher rpms. And not due to actually losing any real low end torque. It will still pull 20mph in top just as it did before.

[chevy-stu]

I don't know if it helps, but on standard Chevy Small blocks (pre LS1's'), 1 3/4 headers are seen to be fine for up to 500bhp... Even 1 5/8 " are acceptable up to 450bhp... I'm sure the LS engines have their own characteristics, but it's easy to over-size exhaust systems on these cars..

[yabadaba]

300bhp/ton said:

As to the primaries - well if you plan on over 500bhp then go for the biggest.

Apart from that I personally don't feel there is much of an issue on which you go for. Both will work and work well. Any difference will not be by any huge amount.

In a race car I can it being important, but in a street car less so.

Thanks for the info/explanation about the relationship between torque and BHP...interesting stuff. These are the two options I'm looking at at present.

http://www.byunspeed.com/compare.php?columns_7285=...

I'll have a word with the mechanic that will be fitting them for me to see if the smaller diameter primaries will be an easier fit. Maybe that will be the decider, given that performance and price seem to be fairly similar on both.

[300bhp/ton]

yabadaba said:

300bhp/ton said:

As to the primaries - well if you plan on over 500bhp then go for the biggest.

Apart from that I personally don't feel there is much of an issue on which you go for. Both will work and work well. Any difference will not be by any huge amount.

In a race car I can it being important, but in a street car less so.

Thanks for the info/explanation about the relationship between torque and BHP...interesting stuff. These are the two options I'm looking at at present.

http://www.byunspeed.com/compare.php?columns_7285=...

I'll have a word with the mechanic that will be fitting them for me to see if the smaller diameter primaries will be an easier fit. Maybe that will be the decider, given that performance and price seem to be fairly similar on both.

Coolio

[ringram]

LS1's will gain a good bit with a tune actually. Take a look at the spec's 98 camaro was rated at 305bhp, 2001 I think 315, but the 2005 HSV R8 was rated at 380bhp. So if you are stock, you are a way off from optimal. Also your intake being an LS1 intake is keeping 20bhp off you. if you do a search on the LS6 intake (google) you will see its a nice and easy swap for more power.

Id wait until you get all your bolt on's installed though before a tune. Each mod can affect both the fueling and timing requirements.

If you fancy an LS6 intake let me know I have one up for sale It was in the Chev part section recently. The LSx series of engines can make some pretty awsome power with minor mods.

[300bhp/ton]

ringram said:

LS1's will gain a good bit with a tune actually. Take a look at the spec's 98 camaro was rated at 305bhp, 2001 I think 315, but the 2005 HSV R8 was rated at 380bhp. So if you are stock, you are a way off from optimal. Also your intake being an LS1 intake is keeping 20bhp off you. if you do a search on the LS6 intake (google) you will see its a nice and easy swap for more power.

Id wait until you get all your bolt on's installed though before a tune. Each mod can affect both the fueling and timing requirements.

If you fancy an LS6 intake let me know I have one up for sale It was in the Chev part section recently. The LSx series of engines can make some pretty awsome power with minor mods.

I'm interested in the LS6 intake.

[yabadaba]

ringram said:

LS1's will gain a good bit with a tune actually. Take a look at the spec's 98 camaro was rated at 305bhp, 2001 I think 315, but the 2005 HSV R8 was rated at 380bhp. So if you are stock, you are a way off from optimal. Also your intake being an LS1 intake is keeping 20bhp off you. if you do a search on the LS6 intake (google) you will see its a nice and easy swap for more power.

Id wait until you get all your bolt on's installed though before a tune. Each mod can affect both the fueling and timing requirements.

If you fancy an LS6 intake let me know I have one up for sale It was in the Chev part section recently. The LSx series of engines can make some pretty awsome power with minor mods.

I've already got an LS6 intake. Mine's a 2001 model so came fitted as stock. Thanks anyway.