Lexus IS Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
612 Posts
Discussion Starter · #1 ·
As many of you know, I have a Toyomoto Stage II with some additional add-ons. To sum it up, here's a quick list:

T-70 with 0.68 A/R on turbine housing
Cast iron manifold
Greddy EVO cat-back
No cats
Siemens 550 cc injectors
Supra tt internals
Haltek e6k
MSD ignition
Spearco fmic
e-shift with valve body upgrade

Last dyno was in Dallas at 110 degrees w/o a fan and I put down 412 rwhp and 383 rwtq at 16.5 psi. This was STD non-corrected hp [same as what Toyomoto, PHR and PFS use for dyno purposes].

Since I've had the car in Dallas, I've pretty much destroyed anything that's come my way, including a Viper ACR, a supercharged Z28 and a few bikes. So needless to say, I'm VERY HAPPY with the top end of this car. But sometimes I feel that I could use a bit more torque at the low end and I've considered various options:

I have discussed and narrowed it down to the following TWO Options:

1) Keep my current T-70 setup, and get more out of it by tuning the Haltek to allow more boost with 93 octane and get a torque converter with 3200+ stall speed. This way, I will get a quicker response and when the boost comes on, it’ll be REALLY STRONG

Pros:
The T-70 has a lot of top-end potential
Cost will be limited to torque converter + tuning time

Cons:
T-70 (according to some) is too large for this car and does not operate efficiently at 16 psi levels. Needs to be run at over 21 psi in order to operate in its “sweet spot” and this will require bigger injectors (i.e. 720 cc) and possibly water/alcohol injection or mixture of race gas. Check out moreboost.org http://www.moreboost.org/turbo_notes.htm#T70

- OR -

2) Get rid of T-70 and get quicker spooling turbo such as Garrett GT40 ball bearing or something similar that has full boost by 3300-3500 rpm instead of my current full boost at 4300 rpm.

Pros:
Much quicker response
Will operate more efficiently at lower psi such as 14
Will be very quick when coupled with a torque converter
More suitable for daily driving

Cons:
Costly
May not produce top-end of T-70 (one of my questions)
Will lose money on T-70 sale

The above is basically a summary of what I’ve gathered over the past week or so, but now I have several questions that I would really appreciate detailed answers to:

1) Is it true that a smaller turbo will yield more rwhp at lower psi levels because it’s operating within its efficiency range, explain?

2) What is meant by top-end? Is it top speed or higher rpm hp? If it’s top speed, then I shouldn’t worry about it since the IS300 is limited to 140mph anyway so there is no sense in having a big turbo capable of producing high hp needed for top speed, right???

3) Will a quick spooling turbo really give me a quicker take-off, or is this again an automatic transmission issue that can be cured with a high stall speed torque converter?

4) If I keep the T-70, can I really run higher boost to get into the turbo’s efficiency range and still be able to run 93 octane by re-tuning the Haltek? I would think so, because increasing the boost on the T-70 to 20 psi may actually produce the same CFM airflow as running a smaller turbo at 16 psi. Thus, 20psi on T-70 may be the same as 16psi on T61, right???

5) How much is my exhaust and cast-iron manifold hurting me in terms of boost response? Will changing to a 3-in exhaust and tubular headers make a difference on the low-end?

6) What does the A/R really mean? I’ve seen much smaller turbos with a lager A/R than what I have (i.e. I have 0.68 and I’ve seen a GT35 with 0.70 and 0.81). What’s all that mean anyway?

So, these are my questions and I would really appreciate some detailed answers. So for all of you who busted your ass in engineering school or you gurus who have acquired your knowledge through experience, here’s your chance to finally put it to good use and enlighten all of us with your wisdom. I’m not being sarcastic; on the contrary, I’m truly looking forward to your responses.

Thank you in advance for your time, effort and assistance. 8)
 

·
Registered
Joined
·
2,710 Posts
From one Toyomoto Customer to another....Go like me and Freelance did...PT67 turbo....ITS badass.....Im very surprised you even went the T-70...I spoke to Lance bout the T-70 and he lead me away form it and to the PT-67 for a bigger turbo that spools quicker...I can quarantee you Freelance loves it as much as I do....I am running a Turbular Turbo Manifold ...tho i have driven both and have not seen huge diff between the cast and turbular unless you just want a higher dyno #.....I do think its sounds louder and beefier with the tubular tho....
-Matt
 

·
Registered
Joined
·
612 Posts
Discussion Starter · #3 ·
UnVme said:
From one Toyomoto Customer to another....Go like me and Freelance did...PT67 turbo....ITS badass.....Im very surprised you even went the T-70...I spoke to Lance bout the T-70 and he lead me away form it and to the PT-67 for a bigger turbo that spools quicker...I can quarantee you Freelance loves it as much as I do....I am running a Turbular Turbo Manifold ...tho i have driven both and have not seen huge diff between the cast and turbular unless you just want a higher dyno #.....I do think its sounds louder and beefier with the tubular tho....
-Matt
It's funny you say that but Lance is the one who put the T-70 in there... I didn't ask for it!!! I think he was just trying it out to see how it does.
 

·
Registered
Joined
·
4,019 Posts
Amr, I agree w/ Matt, the PT-67 would be a better choice for what you want, but make sure you know what you want and your goals arn't set higher than what is feasible. Also keep in mind your numbers will change and don't forget, a normal stg2 produces in the 400's, you dynoed at 515rwhp, I'd say you got a pretty dam good bang for your bucks...
 

·
Registered
Joined
·
612 Posts
Discussion Starter · #5 ·
Freelance said:
Amr, I agree w/ Matt, the PT-67 would be a better choice for what you want, but make sure you know what you want and your goals arn't set higher than what is feasible. Also keep in mind your numbers will change and don't forget, a normal stg2 produces in the 400's, you dynoed at 515rwhp, I'd say you got a pretty dam good bang for your bucks...
Randy, No Doubt about that!!!

Don't think that I don't like it... I LOVE it!!!

I'm just trying to get a quicker 0-60 time, because I'm trying to prepare my car for autocrossing and I've got a little too much lag with the T-70 and no torque converter. So, maybe the PT67 is the best compromise between fast response and top end. I know it's a no brainer for me to get a GT25 and go autocross, but my car would be really weak on the top-end and I'd have no chance at running a decent 1/4 mile. So, I'm trying to find the best of both worlds and it may be very difficult!

I'm just trying to do exactly what you suggested... do my reseach and know what I want before calling Lance and doing it.
 

·
Registered
Joined
·
4,019 Posts
Freelance said:
Amr, I agree w/ Matt, the PT-67 would be a better choice for what you want, but make sure you know what you want and your goals arn't set higher than what is feasible. Also keep in mind your numbers will change and don't forget, a normal stg2 produces in the 400's, you dynoed at 515rwhp, I'd say you got a pretty dam good bang for your bucks...
Onyx_is said:
Randy, No Doubt about that!!!

Don't think that I don't like it... I LOVE it!!!

I'm just trying to get a quicker 0-60 time, because I'm trying to prepare my car for autocrossing and I've got a little too much lag with the T-70 and no torque converter. So, maybe the PT67 is the best compromise between fast response and top end. I know it's a no brainer for me to get a GT25 and go autocross, but my car would be really weak on the top-end and I'd have no chance at running a decent 1/4 mile. So, I'm trying to find the best of both worlds and it may be very difficult!

I'm just trying to do exactly what you suggested... do my reseach and know what I want before calling Lance and doing it.
I got ya bro. Ok here a thought out suggestion. Get the tq converter, than see how that does before you spend the $$$ on somthing else. That may fix what your trying to fix. Also 60ft times in a IS arn't great regardless if the car is boosted or not. I think the best 60ft time on a track that I saw, was PFS w/ a 1.7 but that was w/ slicks or drag ET's.... and thats DAM good considering 1st and 2nd gear, which 2nd is really overdrive.
 

·
Registered
Joined
·
2,710 Posts
TC is the way to go first...this car not boosted or boosted is still more of a top end car...Screw the low end...Youll be the one waving at them in the top of 2nd gear....
-Matt
 

·
Mr. Negative
Joined
·
12,388 Posts
I've been thinking about this some too since we talked and I really need to look at some compressor maps.

Does anyone have some map points for airflow in lb/min at different RPM's so I don't have to calculate it. :oops: Sorry if I'm a tad lazy.
 

·
Registered
Joined
·
1,308 Posts
Hi

I would definitely get rid of the T-70 if you want better performance. A GT-37 and GT 40 as you had asked about would probably be perfect for what you want if what you want is acceleration at the low end. The PT-67 is definitely a good alternative too since people have tried and seem to like it. If you go with the GT 37 or GT 40, I would probably pick a larger A/R .69 would be way too small and restrictive. I have a BB GT40 with a .96 A/R (HUGE) that I will trying on another car. I am a little surprised at how small of an A/R your T-70 has ... I guess I shouldn't be since this is very popular with Supras, certainly it will help you spool faster. Reading maps and stuff is a good start, putting the turbo on in reality is where the rubber hits the road ... or burns :).

If what you're after is overall power then get a nice big turbo! If not then a smaller GT series would be nice.

With regard to the exhaust a 3" is definitely a good idea (all mandrel of course), but you may want to consider an electric cut out that can bypass your entire exhaust system altogether is you want to keep your exhaust nice and quiet for daily driving and open it up for some fun. It's cheaper than getting a whole new exhaust and you get to keep your current catback

I don't think your cast iron manifold will hurt you much in terms of response, the runners are nice and short with good hot gases to spool that turbo. It probably just hurts your top end because of restrictive flow. Having said that though, a tubular manifold that has each runner feeding into the turbo directly rather than run into the same main runner should yield better results. A split housing should work pretty well in theory but no one has proven this in practice on the IS300. PFS uses a split housing, Toyomoto does not. SRT ???. A tubular manifold, unless it is made by the Japanese WILL crack after a while .... choose your poison wisely!

Because you're an automatic, it is easier for you to stay in the high revs where the power band is for a lot of turbos. Don't know too much about automatics since all my cars have 5 speeds, but I believe if the Haltek can control the shift solenoid to shift faster and and maybe harder, that's a start and then the high-stall converter ... sorry don't know much about that.

Just my $0.02
 

·
Registered
Joined
·
12,082 Posts
IS_Dude said:
I've been thinking about this some too since we talked and I really need to look at some compressor maps.

Does anyone have some map points for airflow in lb/min at different RPM's so I don't have to calculate it. :oops: Sorry if I'm a tad lazy.
How is the low-end with your S/C? Your dyno shows maximum torque at a pretty low RPM......you like?
 

·
Mr. Negative
Joined
·
12,388 Posts
Norcal IS300 said:
IS_Dude said:
I've been thinking about this some too since we talked and I really need to look at some compressor maps.

Does anyone have some map points for airflow in lb/min at different RPM's so I don't have to calculate it. :oops: Sorry if I'm a tad lazy.
How is the low-end with your S/C? Your dyno shows maximum torque at a pretty low RPM......you like?
not to threadjack, but it's nice. It comes on smooth and really scoots. On excelleration the tires are always on the limit of adhesion so it just hooks and goes.
 

·
Registered
Joined
·
3,155 Posts
low-end torque...
how about increasing the displacement?
via Jun 3.3L stroker kit or other displacement upgrades? it'll also help to spool more quickly.

my 2cents :wink:
 

·
Premium Member
Joined
·
4,548 Posts
blueIS said:
low-end torque...
how about increasing the displacement?
via Jun 3.3L stroker kit or other displacement upgrades? it'll also help to spool more quickly.

my 2cents :wink:
Toyomoto has a 3.2 stroker kit btw... :wink:

He would most likely go with that i would assume.
 

·
Registered
Joined
·
612 Posts
Discussion Starter · #15 ·
IS_Dude said:
I've been thinking about this some too since we talked and I really need to look at some compressor maps.

Does anyone have some map points for airflow in lb/min at different RPM's so I don't have to calculate it. :oops: Sorry if I'm a tad lazy.
Ok, check out this PDF link... then you HAVE TO CALL ME and let me know what you came up with!

http://www.agpturbo.com/catalog.pdf
 

·
Registered
Joined
·
4,019 Posts
Kanine21 said:
blueIS said:
low-end torque...
how about increasing the displacement?
via Jun 3.3L stroker kit or other displacement upgrades? it'll also help to spool more quickly.

my 2cents :wink:
Toyomoto has a 3.2 stroker kit btw... :wink:

He would most likely go with that i would assume.
its a 3.3L
toyomoto website said:
* Optional: Toyomoto 3.3 Stroker Kit, $5,000
 

·
Registered
Joined
·
612 Posts
Discussion Starter · #17 ·
GTE can't post from work due to a firewall issue, but he sent me this PM and ok'd that I post it for everyone's info....

Thanks GTE for the excellent technical info... you really are a "GURU" :)

hey, i can't post, so here is a pm, feel free to post this for me if you like


1) yes, different impeller sizes and designs compress different volumes of air efficiently, boost pressure on the same motor (all other constant) is directly proportional to volume, with a variable being air compression efficiency and how it is heated.

2) top end is a poor descriptor of how efficient the turbo is at providing air at higher rpms, the more rpms turned, the more air needed at a given time interval, if the turbo cannot keep up, or it is outside of its efficiency range, performance will be less than optimal

3) a smaller turbo will give you better response, but its a trade off, you will loose higher power and efficiency potentials. a torque converter can solve certain acceleration issues

4) i don't know if your figures are correct, but your general logic is. this is possible because octane is related to resistance to cylinder pressure and temperatures. if you can keep cylinder temperatures lower in one scenario, when compared to another, you have the ability to increase cylinder pressure. as for how much, there are too many variables to cover that with a blanket statement for all situations/configurations

5) the three inch exhaust will help response, the tubular header will hurt response (or low end torque) at your power level. its all about flow vs velocity

6) a/r stands for area radius, its actually a divisor that comes out to a decimal, i don't have a diagram to show you how it is measure, but that can be found in corky bells maximum boost i think (i've never read the book so i am not 100% sure)

-gte
 
1 - 17 of 17 Posts
Top